Sergey Kasparov, A Cunning Chess Opening for Black. New in Chess, 2015. 334 pp., $26.95/€24.95.
Technically, it's not the Philidor that Belarusian GM Sergey Kasparov* is promoting in this book, but the Pirc line 1.e4 d6 2.d4 Nf6 3.Nc3 e5 which only transposes to a Philidor in case of 4.Nf3 exd4 or 4...Nbd7 (he gives both moves). Before that, White can vary with 4.dxe5 dxe5 5.Qxd8+, 4.Nge2 or the rare 4.f3, each of which is examined in some detail.
This is not an especially popular opening, to be sure, but it's not a bad one. Black's overall score with this isn't terrible, and just to single out 2014 and 2015 it has been used by many 2700+ GMs including Fabiano Caruana, Maxime Vachier-Lagrave, Vasil Ivanchuk, Dmitry Andreikin, Baadur Jobava, Richard Rapport, and Alexander Moiseenko.
On the other hand, Black's score lately in high-level games hasn't been great, especially in the main line 4.Nf3 Nbd7 5.Bc4 Be7 6.0-0 0-0 7.a4. Initially I was going to check Kasparov's recommendations with what has been happening in top games, but a strength of the book is that there really isn't any such thing as Kasparov's recommendation, singular. He looks at lines with 7...c6, with and without captures on d4 and with and without ...a5. He also takes a (short) look at 7...b6, not to mention sidestepping all of this with early captures on d4 (on move 4, on move 5, etc.). Sometimes after the swap the Black knight goes from d7 to b6, and sometimes not.
Thus this isn't really a repertoire book, but a wide-ranging investigation of a system - or a swamp, as Kasparov jokingly labels it in the introduction and in the book's subtitle. Kasparov is a good guide, too, having played both sides of this opening for well over a decade. He writes with infectious enthusiasm as well, so if you need encouragement from your writers Kasparov is your man. Another attractive feature of the book is a set of 35 multiple-choice exercises. It would be better to have the multiple choice options on a separate page for hints, but even so the exercises are useful for the reader trying to consolidate the material. (And on current pedagogical theory, it's smart to try to solve them first.)
I'll stop short of recommending the opening, and because I'm not entirely sure about recommending the opening it would be strange to recommend the book. What I can say is that if you are interested in the opening, or have had a difficult time understanding it when you've faced it with the white pieces, this is certainly a book you'll want to purchase.
* Despite the last name, his grandmaster title and the fact that he was born in Baku, Azerbaijan, he is of no direct relation to Garry Kasparov.