When Oxford University Press launched their multi-volume "A Linguistic History of English", they started from the very beginning. This first volume, written by Don Ringe, is titled FROM PROTO-INDO-EUROPEAN TO PROTO-GERMANIC, and covers over its four hundred pages two reconstructable ancestors of English. While the series as a whole may interest a different crowd or crowds, this first volume is a major event for Indo-Europeanists. Ringe presents a complete view of Proto-Indo-European according to the current consensus of scholars, surpassing the other, more dated handbooks on the market.
Ringe has been greatly inspired by the work of the late Warren Cowgill, and in many respects his view of Proto-Indo-European is like that of Sihler in his NEW COMPARATIVE GRAMMAR. Ringe believes Anatolian split off early, and the other early IE families are descended from a "North IE" branch, which he focuses on in this work. This allows him to present the verb system as it is easily reconstructible from the bulk of the early IE languages without having to complicate the issue with the very different Anatolian verb. The entire first half of the book is dedicated to a contemporary reconstruction of Proto-Indo-European. All the recently discovered etymologies are here, such as the verb "to listen" being a compound "(s)he is sharp-eared".
In the second half, Ringe exhaustively describes how PIE changed over time into Proto-Germanic, describing the major sound laws and seismic shifts in the verbal system. The new inflectional classes that arose are given in detail. Finally, Ringe takes a synchronic look at Proto-Germanic, comparing its phonological inventory to that of other languages, and conjecturing what allophones each phoneme may have had. I do wish there were more on the Proto-Germanic lexicon than the page and a half here, and this is my only real complaint about the book.
Ringe has maintained correspondence with today's other eminent Indo-Europeanists, and his book includes a number of ideas which, though hitherto unavailable in print, have been floating around in e-mails for some time. Also, though Ringe generally sticks to the consensus view in his reconstructions, he occasionally expresses his own opinions on matters, and these are often thought-provoking. For example, for the ancestor of English "bear (animal)", Ringe would posit PIE *gwer "wild animal" (cf. Gr. ther, Latin ferus) instead of the usual conjecture that it is from a tabooistic circumlocution meaning "the brown one".
If you are new to comparative Indo-European linguistics, this work will probably be hard going. I'd recommend Lehmann's THEORETICAL BASES for a friendly introduction. And those looking for a history of English that includes Proto-Indo-European, but not to the level of detail that Ringe gives, try Roger Lass' concise OLD ENGLISH: A Historical Linguistic Companion. Nonetheless, if you have experience in the field of IE linguistics and like to keep up with the most recent developments, Ringe's book is something you must seek out.