Note: if you have read the author's book on St Clare already, this might not be essential if you just want the basic bones of this form of prayer (contemplation of the Cross), but might be useful if you want a bit more - both are recommended anyway.
But about the book: although I had to concentrate a bit while reading this (happens sometimes when I read books), it gave me a good idea how contemplation of the Cross can change a person and make him a better imitation of Christ, moved more to charity towards people and nature, marvel more at the nature and the whole universe, and more moved towards (creating more) peace.
So I recommend it. :)