Nothing is as motivating as being told "your doing it wrong" when you know you are doing right. On that note, we proceed onto the 5th entry in The OSR for the Lapsed Gamer series of posts.
May we present to you Dark Dungeons.
No, not the Dark Dungeons of Jack Chick fame, which is what you will probably think of if you were gaming in the 80's and 90's, and not the soon to be released movie of the same title based on the original Dark Dungeons comic tract.
I'm talking the Dark Dungeons retroclone, a restatement of the D&D Rules Cyclopedia, not that you'll see that mentioned anywhere in the work itself or the website where you can find the download.
The D&D Rules Cyclopedia was itself a rewrite of BECMI, mostly without the I if I recall correctly. The I is mostly here.
Race as Class is one of the defining features. Your classes are Cleric, Dwarf, Elf, Fighter, Halfling, Magic-User, Mystic and Thief. I had a brain fart with the Mystic class until i realized it was the Monk class. No idea how it was named in the Rules Cyclopedia and my copy is hidden on a shelf somewhere.
For sheer size Dark Dungeons gives OSRIC a run for the money, coming in at nearly 350 pages. It includes rules for mass combat, ship to ship combat, foraging, skysailing, advice on encounter balance, questing for immortality - even if you weren't planning on using Dark Dungeons as the ruleset for your next campaign, there is a ton of interesting stuff to steal borrow for use with the OSR ruleset of your choice. It's also a complete ruleset on it's own.
Dark Dungeons (Free PDF in 3 different formats for computer viewing, printing professionally and printing at home - at 345 pages who the fuck is printing this at home? / Print SC $14.67 / Print HC $26.26 / Print Deluxe HC $89.95)