If you're looking for a standard biography of Shakespeare then this definitely isn't it: Shapiro eschews the usual methods of writing a life and instead concentrates on a single year in Shakespeare's life.
He examines what was happening politically and culturally and how those events both manifest in the plays Shakespeare was writing that year, and also how they might have affected his future work. As he admits himself, this is mostly speculation and cannot ever be confirmed, but it's an imaginiative and original approach which works excellently.
Shapiro examines the 4 plays written in 1599 (Henry V, As You Like It, Julius Caesar, and Hamlet) and relates them to both Shakespeare's (assumed) thinking and external events. He re-reads the plays themselves in light of this and makes some excellent points. But this isn't a 'lit crit' book: it also delves into religion, Shakespeare's possible relationship with his wife and family back in Stratford, the Elizabethan theatrical world, and Elizabethan politics.
The one major gap for me was an exploration of the sonnets written around this time, and the (possible) implications for Shakespeare's personal life. There's nothing here about his emotional life (which admittedly would be pure speculation - but then a lot of this book is). That small caveat aside, this is an excellent, well-written, and entertaining book, as rewarding, I would guess, for the non-specialist as the specialist.