The Old School Renaissance Handbook has been released by Brent Newhall. It is a concise summary of 16 roleplaying games that are considered by many as part of the OSR. One helpful feature of the comparisons is that he reproduces the same set of five characters for each of the systems. He also wrote some commentary on what he feels the OSR is about. It definitely not a definitive survey of the various retro-clones and old school games but very well done. I hope he does a followup on some of the games he missed in the initial release as well as one on adventures and supplements.
Note also that he is planning on publishing a book with some additional material contributed by various notable OSR authors and publishers like James Raggi of Lamentations of the Flame Princess.
One final bit of commentary here, it is easy to knock stuff like this as hubris or trying to define the OSR. I for one welcome this kind of material as it can help newcomers get a sense of what is a glorious mess. I would encourage anybody with the interest in writing this type of material to do so and get it out there. The only caution I give is that whatever you write about the OSR remember it is only your viewpoint. In my opinion as of 2013 the OSR has grown so large and diverse that any of one of us only hope to cover a small fraction of what out there.
Just Look at the Horde and Hoard list which show over 700+ products as of May 2012 and that list was compiled just from those OSR that were designed specifically to work with a classic edition. Add the ones that are old school feel, and classic edition variants we are looking at a couple of hundred more.
Here to 2013 to being another banner year for the OSR.