Yeah I already have that one.
If you liked Contents Under Pressure and care to know more about their history, there are a few more books (most of them out of print) that you can try and track down.
Rush - By Brian Harrigan (covers to 1982)
Success Under Pressure -- By Steve Gett (covers to 1984)
Visions -- By Bill Banasiewicz (I probably butchered that....covers to 1987)
Mereley Players (Yes, it's spelled wrong, unbelieveably went to press like that) -- By Robert Telleria (Compilation of various referencial details...many of which are wrong up to 1997)
Chemistry -- By Jon Collins (Covers up to 2004; does not directly interview the band, but people who have worked with the band)
Of course all of Neil's books (The Masked Rider, Ghost Rider, Traveling Music and Roadshow), shed a little light on Rush (sometimes very little) in varying degrees of detail.
If you are looking for lyrical interpretations, two books I have are A Simple Kind of Mirror By Leonard Roberto, Jr. which covers lyrics from Permanent Waves To Test For Echo and Mystic Rhythms - A Philosophical Vision of Rush by Carol and Robert Price which covers lyrics from 2112 until Presto, but includes discussion up to Test For Echo.
There is also Rush, Rock and the Middle Class which attempts to put the Rush experience in some kind of understandable context.