This book is the second edition of Desktop GIS: Mapping the Planet with Open Source Tools, so all the good reviews are still true for this uptodate edition. the author is an expert of this topic and the founder/creator of the (imho) best free opensource gis: QUANTUM GIS.
So why just 4 stars? Well, on the books website under changes between first and second edition you can read: "A short discussion of the SpatiaLite spatial database is included." This is not the case, because this "short discussion" (chapter 9.6) is less than one full page(!) and is only an "announcement", that you can use spatialite with qgis. (If the free and open-source spatialite would be sold as a commercial product, the company would give more info in the product-flyer/info-brochure than there is in the book!) so this is a great disappointment,because qgis is the first (and only?) opensource gis, which has native support for spatialite and learning from the auhor how to use spatialite (with qgis) would have been very fine...
So - in my personal opinion - a great book, but no "real" info about spatialite. If you do not already own a copy of the first edition its definitve worth buying