Completely different in almost every way!
Spark to Icon, and the earlier version Sound and Vision, are produced by B&O and are lavishly produced very large books full of wonderful photos and a commentary of the company from its inception to modern day. Not much detail on the individual products but gorgeous. A few inaccuracies but highly recommended.
The Crowood Collectors Bang & Olufsen was written and produced by the Jarman brothers who run the excellent Beocentral site. (I should declare at this point that they are friends of mine and hence I cannot be described as unbiased). This book canters through the early products and then concentrates on the products since the 60s till about 2000. It describes a lot of the products in good detail with excellent pictures and has chapters on maintaining, restoring and building a collection. Excellent book but both volumes serve a different purpose. Essentially you need both!! 