A timely publication to tie in with the seventy-fifth anniversary of the New Deal and it's a worthwhile addition to the only other book on the subject: Christopher DeNoon's `Posters of the WPA' (ISBN 0295965436).
Ennis Carter has edited a lovely book of almost five hundred posters, divided into twelve sections. Though there were thousands produced the selection here will give you a good idea about the style and themes. Having looked through the book several times I feel there a couple creative styles shown in the posters: the solid colour modernist ones with their angled headlines in geometric type promoting industry and the more whimsical folksy ones for art shows and plays. All of them reflect what is possible with the cheap silkscreen process so there is an absence of photos or anything that required a graduated tone. Fortunately the technique more or less makes artists and designers go for something simple and direct using two or three colours.
Most of the posters use silkscreen though I was surprised to see some that were captioned as `Hand painted on board', surely there weren't many produced like this. The cultural event ones had to present a lot of type detail for name of the event, players, location and ticket prices whereas the ones that could be called propaganda presented a straightforward message: Careless talk costs lives!
The book's production is first class with good paper and printed with a 175 screen and nicely all the posters have a drop shadow which lifts them off the page. I think Christopher DeNoon's book (out of print but worth searching out because the price seems to rise yearly) is the one I prefer, though it has a lot fewer posters, 280 in colour, it benefits from several excellent essays about the WPA background to the times plus it's beautifully designed.
Both books will probably be the only ones ever published about WPA posters and they both cover the subject beautifully.