The BBC book 'The Crusades', co-written by Alan Areira and Terry Jones of Monty Python fame, is certainly entertaining, accessible and a nice book aimed at the beginner. It isn't particularly detailed, does repeat a few popular 'myths' that aren't widely accepted any more, but for a first book I'd thoroughly recommend it.
If you finish that one and fancy something with a bit more meat (not to mention accuracy) then I wouldn't hesitate to recommend any of Thomas Asbridge's books.
"You're a big man, but you're in bad shape. With me, it's a full time job." – Lt. Bromhead to Prince Dabulamanzi before the Battle of Rorke's Drift.
Yes definitely the Ian Heath one - if you can still get it.
Also, 'A complete illustrated history of the crusades and the crusader knights' (and.... breathe is not too bad for an over view. HH publishing 256 pages. Charles Philips and Dr Craig Taylor. It covers all the crusades (inc baltic/lithuania) up to 1570.
VIRTUTIS GLORIA MERCES -- Glory is the reward of valour.