As always THE go to reference source for policing and criminal law. Essential read's if you are studying for ospre part 1. For student officers I would suggest the Blackstone's Student Officer handbook. These books are very thorough and my only criticism of them is at times they can be very hard going to read. However, studying these in combination with the online Q&A's, be it Blackstone's or ical you can't go far wrong for the exam.
Personally I feel they could be improved upon with a bigger summary section which includes more case law to round off a particular topic. Something like the main chapter for the full read and the conclusion as a revision crammer. Though crammers can be bought and are generally very good, considering the price/size of the books I feel they could integrate one more. This review although tagged under the 2006 edition is applicable to all so far as I have had the 2006 and 2009 editions. The only real change being updated legislation.