I used to love the Fighting Fantasy books as a kid. I had several dozen of the things and loved going through them. I wasn't really interested in the faff of actually rolling dice and fighting things though so I just cheated
After I had been through a book a few times I would have a lot of fun trying to deconstruct the whole system, going through every possible branch to find out exactly what made the whole thing tick.
The series was also my first real introduction to fantasy literature (and art!). Geek culture wasn't really a thing where I grew up and I had a small friend group so the usual routes like D&D or Warhammer were not available to me. Instead I had the Fighting Fantasy books, and they were awesome. They even had their own RPG
rule book, lore compendium and manual of cool and gruesome monsters.
Particularly memorable titles (spoilers for some):
Curse of the Mummy: My first ever Fighting Fantasy book. Cool settings, awesome monsters and an exciting story.
Return to Firetop Mountain: Possibly the best example of a classic fantasy adventure. Stock up on supplies, travel to a far-off landmark, traverse a twisting dungeon and kill the big bad evil guy.
Knights of Doom: Features the most bad-ass fantasy monster ever conceived: the assassin's dagger. It is a deadly blade wielded by an intangible and indestructible spectral hand. You can keep trapping it but it never stops coming and will harass you at various points throughout the book. If you don't work out a way to banish it for good then it finally catches up with you right after you defeat the final boss
Legend of Zagor: This one actually lets you choose from four different classes, with each one being able to approach problems in different ways.
Revenge of the Vampire: hilariously impossible to complete due to a 'bug'. To beat it you need to steal the codex from the vampire's entourage whilst he stays at the inn. However, you cannot enter the inn without coin and the only way to reach it on time is to pay every last gold piece you own to an opportunistic horse merchant.
Creature of Havoc: You play a mindless beast with no way to communicate and no will of its own. At the start your actions are entirely controlled by random dice rolls. As you blunder through you slowly regain your faculties and try to restore your former self. An awesome concept, although quite annoying to actually play
Magehunter: A crazy book involving the titular magehunter, his young apprentice and a body-swapping wizard. The path to the true ending is ridiculously narrow, requiring that you learn to body-swap yourself and then get everyone back into the right bodies by the end. You can make a decision right at the start that will damn you to failure, but it still lets you continue through hundreds of useless pages before you find that out
Appointment with F.E.A.R.: A modern superhero setting rather than fantasy. You get to pick your powers and then have relatively free-reign to target the villains that you think you have the best chance of taking down. One of the power sets involves both super strength AND flying and so is ridiculously overpowered compared to the alternatives.
The Rings of Kether: A sci-fi setting. My only real memory of this one is that it is the only one that I failed to properly map. Everything branched off like crazy. It also didn't help that there was a lengthy section that involved you piloting a spacecraft by deciding, basically at random, whether to adjust the roll, yaw or pitch in order to avoid enemy fire.