D100 Dungeon

I highly recommend this game for anyone looking for solo dungeon delving (with simple home rule or the official expansion you can also play cooperatively).
As described, following the simple yet clever rules, make a character and go on adventures. Monster encounters, traps, puzzles, treasure! Start with basic quests to gain skills, armor, weapons. Then go on more demanding adventures. The outcome of encounters and other challenges based on dice rolls against your stats and the stats of the monster or trap/challenge. What you encounter and earn generally determined by rolling on various tables. As the name implies the core mechanic is based on d100, and you also use d10 and d6.
Can Print and Play the basic version (V 2.2) completely free.
Version 3.0 is well worth the small fee. Ignore the comments regarding inability to print V 3.0. Everything you need to play is available as a free download; only the core rules for V 3.0 have to be purchased, which seems right to anyone who produces anything.
When you love the game, which is really a game system, and I expect you will, I would highly suggest you consider investing in the expansions. All are great: Adventurers Companion, Tome of Extraordinary Rules, The Dragon Armour. Again, the expansion rule-sets for digital downloads are a small fee, but all pages needed for tracking and play are free to download.
Finally, if you prefer hard copy, the physical books are quite beautiful and well worth the cost, frankly inexpensive in comparison to most books in the RPG world. It is not necessary to buy the physical books. They are just a beautiful addition to a terrific game system, professionally printed and bound.