This is an A-Z of popular music, but it is also a great compendium of one man's mostly perceptive opinions on popular music, and its practitioners.
Some of the entries are replications of Dylan's articles in GQ and IPOD Therefore I Am, but to have them all in one place is great. The entry on Steve Winwood is an absolute pearl, explaining Winwood's greatness from Spencer Davis up to, and including, his most recent solo album.
Dylan's perceptiveness on Frank Sinatra is also excellent, even highlighting how Frank sings, incorrectly, though wonderfully, on his cover of Something, and he also profiles the other singing Rat Pack members with aplomb, highlighting the wonderful, albeit little-known back catalogue of Sammy Davis Jnr, and the laid-back wondrous charms of Dean Martin. I already have some of Sammy Davis Jnr on cd, and would heartily recommend his live album with Buddy Rich, The Sound of 66, even more.
There's also a short perceptive piece on the shadow-zone that is Bob Dylan's Bootleg Series Vols 1 - 3, and the merits of the Infidels Outtake Blind Willie McTell. Furthermore, the wonderfully underrated Americana musician, producer, and Renaissance man, Joe Henry, merits an entry, not just on the production of Mose Allison, Solomon Burke, and Allen Toussaint, but also on his own excellent albums. Consequently, I would recommend people buy Scar, which is Americana combined with jazz musicians such as Brad Mehldau and Ornette Coleman. Dylan's entry on Toussaint highlights what an amazing musician and songwriter he is, and how Toussaint rose to the occasion of his last album, The Bright Mississippi.
There's also another thing, upon which Dylan and I agree, and that is the greatness of Blood & Chocolate, which was one of Elvis Costello's finest albums. To have actually seen Elvis live at this time, would have been an unmitigated highlight, for which I am a tad jealous.
All in all, to conclude, the dictionary is one of the best books written about music of any genre, as it comes from a fan primarily.