I very much liked Neil Powell, Benjamin Britten: A Life for Music. Also very good is Paul Kildea, Benjamin Britten: A Life in the Twentieth Century. They are both also useful for understanding English intellectual life during the 20th century, most of all Auden but even Keynes and also the broader history of homosexuality in England. Both are already out in the UK, where I picked them up earlier in the year, and both will make my best of the year list in late November.
Here is a good Anthony Tommasini survey of Britten at 100. I will offer these bits
The Britten pieces you are most likely to enjoy: Serenade for Tenor, Horn, and Strings, that disc has Les Illuminations and Nocturne too and is the single best Britten disc to buy, and also A Ceremony of Carols.
The ones I think are best: Cello Symphony, Winter Words (song cycle), and perhaps Billy Budd. War Requiem. Nocturne is a powerful spare late work. I like Curlew River for its connection to Balinese music, although I would not put it among his best compositions from a strictly musical point of view.
My most significant Britten heresy: I’ve never enjoyed listening to Peter Grimes and I find most of the experience oppressive. More generally, for much of my life I never felt close to Britten’s music, as it made me crave Stravinsky and Mahler instead. But I’ve listened to it quite a bit since January and have enjoyed it more than expected.
Two points: I think he understood the English language better than any other major composer, and how he sets and understands a text is without parallel, in English at least. Furthermore as a conductor or pianist he is superb, try his Brandenburg Concerti or his piano on Schubert’s Winterreise, Peter Pears singing, among other works. Those are two of my favorite recordings in all of classical music.