It's a diverse set of essays by game designers, both digital and tabletop, as well as by game studies academics. Some discuss tabletop game design, others analyze games they admire, and others talk about other things that impinge on tabletop games. You can read it online, download it in plaintext, or buy either a physical or e-book version from the book's page at ETC Press.
Among the pieces I like best are Stone Librande talking about the games he designs every year as Christmas presents for his kids; Lew Pulsipher on the difficulties in designing three-player games; and John Sharp on Pandemic and why most serious games suck. Ian Schreiber, who sometimes posts here, has a piece on Settlers of Catan. Other contributors include Jim Dunnigan, Dave Parlett, Richard Garfield, Peter Olotka, John Kaufield, Chris Klug, Kevin Jacklin, Ira Fay, Brian Magerko, Simon Ferrari, Matthew Berland, Pat Harrigan, Noah Wardrip-Fruin, Ray Mazza and Brenda Bakker Harger.