I don't know if the google library it charges access to is usable by screen readers or not, but the two ebooks I downloaded from them, both of which were free, were simply scanned images of the paper book nicely bundled into a (I'm sure) pretty looking pdf file.
Not to defend that which Google is doing or not doing, but to point out a "correction" -- not all the books in google library are simply scanned images bundled into a "pretty looking pdf file." On the left side of the google books page that displays a book you have clicked through on because you think you are interested in that book is a tab choice labeled "Read on Your Device." About half the books I see there have the option "eReaders and other devices" which will have the choice you described earlier namely "Download PDF" which indeed is simply a bundle of pretty pictures -- bitmap representations of "Xerox Copies" of each page in the book. But the other option is sometimes "Download EPUB" -- which still has the problem that introductory pages, table of contents continue to only be represented as bitmap "pretty pictures", but the body text has been automagically Optical Character Recognized and converted to electronic text form, which screen readers can hopefully handle -- especially since one can get ePub plug-ins to allow one to read ePub format directly in several common web browsers -- and modern screen readers had better be able to handle modern web browsers. Google has put a lot of work into their in-house OCR engine the last couple years, and while the results are not even up to that of the worse PG books, I find them surprisingly useful for a raw OCR effort. Still, truth be told, I find it easier to read the "pretty picture" bitmap scanned "Xerox Copies" of google books than their somewhat mangled "OCR EPUB" versions. In either case one has to be somewhat motivated to actually read the book in question -- which presumably is something old and obscure -- otherwise one can generally find a "clean copy" of things that are old and *not* obscure already in existence in the PG library. Below find a snippet example of the performance of the google OCR efforts which one can compare to PG books human efforts (compare to William Winter "Shakespeare's England" PG# 35105) -- not all google OCR efforts are this successful, especially when they try to OCR an even older text: ===== PEEFACE. Beautiful and storied scenes which have soothed and elevated the mind, naturally inspire a feeling of gratitude. Prompted by this feeling, the present author has written this record of his rambles in England. It was his wish, in dwelling thus upon the rural loveliness and the literary and historical associations of that delightful realm, to afford sympathetic guidance and useful suggestion to other American travellers who, like himself, might be attracted to roam among the shrines of the mother land. There is no pursuit more fascinating, or in a high intellectual sense more remunerative; since it serves to define and regulate the stores of knowledge which have been acquired by reading, to correct misapprehensions of fact, * to broaden the mental vision, to ripen and refine the judgment and the taste, and to fill the memory with ennobling recollections. These papers, accordingly, since they aim to encourage this pursuit, are at least creditable in design, however defective they may be in execution. They were addressed more particularly to American than to European readers. They commemorate two separate visits to England, the first made in 1877, tJte second in 1882; they occasionally touch upon the same place or scene as observed at different times; and especially they describe two distinct journeys, separated by an interval of five years, through the region associated with the great name of Shakespeare. Repetitions of the same reference, which now and then occur, were found unavoidable by the writer, but it is hoped that they will not be found tedious by the reader. Those who walk twice in the same pathways should be pleased, and not pained, to find the same wild-flowers growing beside them. The American edition of this work is comprised i> two volumes, published at Boston, called "The Trip to England" and "English Rambles." ....