I bought Hugh Foster's "Biscuit Joiner Handbook" at a firesale at the local bookshop and read it from start to end. Foster's book is about the biscuit joiner as a machine, how it operates, and outlines the different kinds of joints one can create.
Next, I bought Jim Stack's book and I was pleased because it has lots of project examples that showed me where and how, in many different types of wooden furniture construction, I could apply biscuit joinery. This is the kind of information Hugh Foster's book does not have. As a result, I was able to pick up a Furniture & Cabinetmaking magazine, look at a project for a blanket chest that had 20+ mortise and tenon joints, and figure out how to replace those joints with biscuit joints!
The other benefits from the book were the good, sharp photographs; Hugh Foster's book has black and white photographs that are murky and indistinct and I had trouble distinguishing the workbench, the wood and the tool in lots of the photos
I did not give Jim Stack's book higher stars because there are a few subediting mistakes (e.g. wrong project and steps used in cross references - its annoying to be directed to project "x" to see how to do something when project "x" does not show this), I think it lacks an end-to-end example of how to make a panel door using biscuits and the (to me) dangerous examples of the use of circular saws (no riving attachment, no cover over the blade, fingers awfully close to the moving blade) and the jointer (fingers too close to the moving blades). I would have found the last acceptable if there had been a notice at the front saying the riving attachment and cover had been removed temporarily to make the pictures clearer.
Lastly, a suggestion for the next edition. Please add in the warning that the biscuit joiner must be up to full speed before the plunging is done in order to prevent kickback and cutting your hand - there is a nasty accident detailed on the Internet somewhere (Mick's Woodworking Tools page???) that was caused by the person plunging before the machine was at full speed.
Summary: complements Hugh Foster's Biscuit Joiner book really well, buy it for the examples of when and how to use, be aware of the dangerous circular saw and jointer photos.