The errata books on books series, as I understand it, are re-productions of important, out-of-print, rare - and therefore expensive - photobooks. I've spent some time with the first four, and they are done with intelligence, care, and seemingly with love for the work. Of course there's no substitute for the original editions, but that's sort of the point. The idea is to take each first edition seriously as a work of art, treat it with deference, make the work available to a wider audience, and add something to the mix in the form of a new essay and background information. Taking this first batch as indicative, there will be no fluff in this series -- the first four choices are powerful and interesting, both individually and in combination. Don't misunderstand: if you're considering selling your car and using the money to buy first editions of In Flagrante, Fait, etc. and a bicycle, well, that just might be a wise move and I admire you. Probably I should do exactly that. Until then, we're fortunate to have these books, and I look forward to more.
For what it's worth, you don't have to take my word: Parr & Badger each mentioned errata books on their `best of 2008' lists.