Summoners are a particularly interesting addition to the roster of character classes available for Pathfinder players. The Introduction states the purpose of this book, to provide carefully-designed feats chosen to make the most of the special abilities of this particular class, and - through the suggested 'career paths' - demonstrate how to use them to good effect in constructing effective and interesting characters.
Next is an overview of the summoner and, as always with this series, a good knowledge of the basics from Paizo's Advanced Player's Guide is recommended before you settle to explore the potentials laid out here. Suffice to say, he's an arcane spell-caster specialising in summoning creatures to do his bidding and has one particularly intriging feature: his eidolon. This is a powerful outsider with whom the summoner forms a lifelong attachment, being able to summon it like any other creature except that it can stay until dismissed. It acts in accord with the summoner's wishes but has free will as to just how it goes about it! Fun indeed and in the hands of a creative player far more than an adjunct to combat. Although a regular spell-caster outside of summoning ability, the summoner is relatively weak in this regard and his lists concentrate on defence, enhancement and things related to summoning - such as calling up walls and pits, which can lead to some interesting and unusual battlefield tactics, if that's the way that your summoner is inclined.
So, on to the new feats. Many are available to any character who can meet the requirements, although they are aimed at this particular class. One thought for effective use of an eidolon is to have one which can fly, so feats like aerobatics and balanced spellcaster (which lets you dispense with Concentration checks when you try magic on the move) are of particular use if you have taken that path. One of the most unusual requirements for a feat must be that for multihanded weapon - you need 3 or more arms! (As you can imagine, it's mostly intended for eidolons.) If you take a tactical approach, wall mastery is useful as it permits you to have holes in walls that you have summoned through magic, while enlarge wall lets you have bigger ones than the opposition might expect. Another feat with potential for fun must be clockwork summoning which enables you to summon a mechanical version of the creature you wish to summon. There's one minor problem: in the headings to the feat descriptions, somehow the letters 'ft' - as in shifting wall and sizeshifter do not render correctly, although a quick play with the copy tool shows the right letters are actually there!
Next, three character builds are presented - which for summoners include builds for both yourself and your eidolon. First is the Chess Master, and it's a real gem, using the varied abilities of the Summoner to take control of a battlefield, manipulating the terrain and the movement options available to your opponents to your advantage (and, of course, their detriment). If you enjoy a calculating and tactical approach to combat, this build is worth your consideration. The others are Mythic Rider, based around using your eidolon as a mount, and the Master at Arms, where both character and eidolon are carefully-crafted battle-monsters, fighting side-by-side! The work rounds off with a 'character sheet' specially tailored for eidolons, as you are going to need to track its capabilities as much as you need to document your own.
Overall, this is a good addition to the series, very combat-oriented but opening out some very interesting possibilities - now to learn all the wall spells I can and take the wall-manipulation feats...