This is a handy, portable guide to opera: composers, artists, national trends. The authors have done a good job of ferreting out information and putting it together. If you just need to check which opera has a prima donna called Isabella (Rossini's L'Italiana in Algeri
) or the definition of a covered tone, this is a good book to grab.
The Oxford Dictionary of Opera:
"The most authoritative single-volume work of its kind."--Indpendent on Sunday