There are literally hundreds of excellent books on volcanoes! 

Some standouts off the top of my head include:

The Encyclopedia of Volcanoes by Stephen R. McNutt, Hazel Rymer, and John Stix (Hardcover – Oct 29, 1999)

Volcano: A Visual Guide by Donna O’Meara and Professor Aubrey Manning (Paperback – Jan 18, 2008)

Volcanoes by Robert Decker and Barbara Decker (Paperback – Oct 7, 2005)

The Volcano Adventure Guide by Rosaly Lopes (Hardcover - February 7, 2005)

Volcanic Worlds: Exploring The Solar System’s Volcanoes (Springer Praxis Books / Geophysical Sciences) by Rosaly M.C. Lopes and Tracy K.P. Gregg (Hardcover – Oct 15, 2004)

Volcanoes by Peter Francis and Clive Oppenheimer (Paperback – Dec 25, 2003)

Volcanoes of North America: The United States and Canada by Charles Arthur Wood and Jürgen Kienle (Paperback – Nov 27, 1992)

Studying Volcanoes / Volcanology