Time Machine Series

If you're looking for the classic novel by H. G. Wells, see The Time Machine.

Time Machine is a series of educational Choose Your Own Adventure books, published by Bantam Books in 1984-1989. Unlike many other works of this genre, the books only have one ending, reached usually by trial-and-error.

The premise is that the player is tasked by some unknown authority to travel to the past in order to unravel a historical mystery. Following a strict set of time-travel rules, the protagonist finds himself skipping back and forth through several centuries of history, braving dangers and somehow always coming across famous historical figures.

The series as a whole displays examples of:
when this part comes in the book, you don't actually have the choices presented by the cover.
 * Can't Take Anything With You: Leaving items from a future epoch behind is one of the things forbidden by the "time travel rules".
 * Changed My Jumper: The protagonist is always careful to take clothes appropriate for his destination; when he time-travels into different eras entirely, some people may casually comment on his weird clothes.
 * Choose Your Own Adventure
 * Continue Your Mission Dammit: The hints occasionally chastise you for even considering certain options that won't bring you closer to your goal.
 * Covers Always Lie: At least in the Polish edition, the back covers sometimes feature a situation from the book and hint that you will have two choices in that situation (and that if you choose wrong, you'll end up stuck in a time loop). Most of the time, ir turns out that
 * The Polish cover for 'Mystery of the Atlantis deserves a special mention: it claims that the Olympic games featured in the book are the first'' Olympic games, something that isn't mentioned in the book... and this claim on the cover is accompanied by a huge headline stating "it's the year 400 BC", while Olympic games actually started at least two centuries earlier!
 * Edutainment Show
 * Groundhog Day Loop: Supposedly, if you break the time travel rules, you risk being trapped in one of these. In practice, an easier way to end up in one is to take the wrong inventory item at the beginning.
 * Since bad choices make you re-read pages you've read already, the protagonist technically falls into a few short loops (with two or three iterations, tops) on his every adventure. (Since some of them involve arduous weeks- or even months-long trips, it's probably not pleasant...)
 * Hint System
 * In Spite of a Nail: On one hand, the rules forbid you from changing history; on the other hand, the protagonist tends to save random people's lives without a thought, even if they would die without his being there.
 * In the Past Everyone Will Be Famous: Your time machine apparently has a mind of its own and a thing for depositing you just at the right time and place.
 * Inventory Management Puzzle: So, you can take a tiny compass... a tiny lockpick... OR a huge unwieldy scary mask, but only ONE of these.
 * Kid Hero: The protagonist. The exact age is unclear, but seems to be somewhere around 13. Which doesn't stop him from people occassionally treating him as someone older for sake of the plot; for instance, he can end up becoming a full-fledged astronaut.
 * Our Time Travel Is Different: Instantaneous Time Travel, apparently.
 * Plot Hole: Sometimes, you can end up reading the pages out of the intended order and the protagonist will end up knowing things he shouldn't.
 * POV Cam: All the illustrations are from the protagonist's point of view.
 * Present Tense Narrative
 * Second Person Narration
 * Time Machine: Gee, ya think?
 * Time Travel
 * Time Travelers Are Spies: Commonly happens to you.
 * Unwinnable By Design: Some books offer you a few items in the beginning, and you have to choose one to take. Usually, choosing the wrong one will get you stuck halfway through.
 * What Year Is This?: Not only that, but the protagonist also tends to be surprisingly oblivious about pretty much everything about the era where he's going. Rarely does this get him anything worse than a weird look.

Search for Dinosaurs (1984)
The protagonist must take a picture of an Archaeopterix, the first bird. Most of the book consists of figuring out where and when the Archaeopterix lived, by hopping back and forwards through the Mesozoic and piecing together information.
 * Apocalypse How: You get to witness the Cretaceous mass extinction, which is a class 4.
 * Big Creepy Crawlies: You meet some impressively large dragonflies in the Triassic period.
 * Everything's Better With Dinosaurs
 * Never Smile At a Crocodile: especially 30-feet Cretaceous crocodiles.

Sail with Pirates (1984)
The protagonist accompanies Captain Phips in the seventeenth century in order to find the wreck of Concepcion, a Spanish ship carrying colossal amounts of silver.
 * Fortune Teller: Old, blind, but oddly knowledgeable black woman who gives you cryptic hints (and is one of the few persons to know about your time travel.)
 * Futureshadowing: The very beginning of the book has you meet a man who mentions meeting you before, and is talking about things you'll do much later (from your perspective), while time-travelling into the past. Strangely, it's possible to finish the adventure without ever actually doing the things the man mentions you doing...
 * Go Mad From the Isolation: The pilot from Concepcion after being alone for a long time.
 * Jerkass: Jim Teal.
 * Pirates

The Rings of Saturn (1985)
An Oddball in The Series, as it sends the protagonist to The Future. This frees the writer from the shackles of historical accuracy, making the book essentially a Troperiffic showcase of pretty much every single Science Fiction trope in the book.
 * Air Vent Passageway: Used to escape from the nasty Space Pirates.
 * Cyborgs
 * Drill Sergeant Nasty: You run into one of these when you train to be an astronaut. If you screw up, you end up reassigned to train elsewhere under an intelligent dolphin. Who's even nastier.
 * Fantastic Racism: Humans fear cyborgs. It's meant to be shown as intolerance, but, interestingly, pretty much all cyborgs you meet on your way are in fact evil.
 * The Future
 * Mad Scientist: Who transports you into Another Dimension against your will.
 * Psychic Powers: Several mutants with a multitude of powers, living in a wildlife preserve. Their powers range from Telepathy through future sight to Teleportation.
 * Robot Dog
 * Sapient Cetaceans: Telepathic dolphin officers, to boot.
 * Space Pirates
 * Terraforming
 * Trailers Always Spoil: The cover depicts.
 * Undead Tax Exemption: Very noticeable in this setting--your address is explicitly said to be years out of date, and you're probably long dead in that era anyway, yet you're able to be enrolled into an elite academy with no problems.
 * United Nations Is a Super Power: And an One World Order, though benevolent.
 * Veganopia: No meat to be seen around, just vegan food.
 * The X of Y

The Mystery of Atlantis (1985)
Travelling through Ancient Greece, the protagonist is trying to find out the mystery of... some place I can't remember right now.
 * Atlantis:
 * Changed My Jumper: Averted; you can time-travel all over the world and all over history, and nobody ever notices you're a kid in an ancient Greek chiton.
 * Future Imperfect: Though not with the future; it is stated that
 * Galley Slave: You can temporarily become this.
 * Something They Would Never Say: If you try and tell a suspicious city guard that you are a Scyth, he will promptly quiz you on a piece of Scythian culture (since he is a Scyth himself.) You fail, at which point he decides you're a runaway slave.

Search for the Nile (1986)
The protagonist heads to the late nineteenth century to accompany Henry Morton Stanley in order to find out what is the source of Nile.
 * Arc Words: "Buala Matari". What's it mean? Why is Stanley called that on his tomb?
 * God Guise: Entirely by accident you end up scaring an African tribe, disguised as a panther-like supernatural being. The shaman isn't fooled though.
 * Great White Hunter: Sir Mortimer P. Quimby III. Subverted - this particular hunter is content merely to track down the animal and aim his rifle without actually shooting, solely for the satisfaction of outwitting the beast.
 * Insistent Terminology: Do not call Henry Stanley "captain". Or else he will... uh... chastise you mildly.

Blade of the Guillotine (1986)
The protagonist finds himself in the times of French Revolution, seeking a priceless diamond necklace. The objective soon shifts from merely finding the treasure to using it to buy the life of an innocent French girl.
 * Blind Alley: Used to escape an angry royalist blacksmith.
 * MacGuffin
 * Riddle Me This: Subverted. When given a cryptic answer about the necklace's location, you have to interpret the "riddle" literally. If you try to be smart and go for the metaphorical meaning, you'll just end up in trouble.
 * The X of Y

Quest for the Cities of Gold (1987)
The protagonist heads to America in the sixteenth century in order to investigate the rumors of the supposed "cities of gold" searched for by the conquistadors.
 * Go Look At the Distraction: Used to escape an Aztec guard to avoid fate of a Human Sacrifice. Not that it will help you if you've ended up in that paragraph.
 * Never Smile At a Crocodile

Quest for King Arthur (1988)
The protagonist travels through ancient Britain, attempting to find the original inspiration for the King Arthur tales.
 * Human Sacrifice: Almost done to you by some druids at one point.
 * Made a Slave: A farmhand for a Saxon.