There's no shortage of Lovecraft-themed tabletop RPGs these days, but for my money Trail of Cthulhu stands out from the pack. As I recommended in our list of alternatives to D&D, it combines a classic and exhaustively researched take on the Mythos setting with innovative mechanics designed to make running spooky mysteries a breeze. What I didn't have space to mention there is that it also has some of the best supplements, adventures, and setting books around—and now, thanks to Humble Bundle, you can pick up nearly the full range for a steal.
For just £14.29/$18, the Trail of Cthulhu bundle includes PDFs of the core book and 19 other books, as well as two soundtrack EPs and a voucher for 20% off on publisher Pelgrane Press' own store, if you want to follow up by buying another of their games (might I recommend Night's Black Agents?). Standouts in the bundle include: Bookhounds of London, a wonderfully evocative campaign setting where you hunt down forbidden tomes in 1930s London; Hideous Creatures, which not only goes into brilliant detail about all the monsters of the Mythos, but also provides tons of material and inspiration for how to actually build mysteries around them; and Rough Magicks, which lets players dabble in inhuman sorceries, most likely dooming themselves in the process…
It's a ridiculously low price for some of the best TTRPG books you'll ever own. I should note, however, that Pelgrane Press has announced that a second edition of Trail of Cthulhu is in the works, with a Kickstarter launch planned for November. It doesn't sound like it'll be making huge changes—it's more about bringing in some tweaks and updates to the rules system from their other games, and making the book a bit more accessible for newcomers to the hobby. So all the content in these books should stay relevant, but just be aware that this is probably a bit of a last hurrah for this edition of the game.
The bundle is available until September 28.