This really is the most up to date coin reference book. It contains list prices and mintage of all the British coins since the late 18th century including a section on proof coins. Included are informative articles on grading coins and a little bit of history on each denomination. There's a section on decimal coins, gold coins, rare proofs and some pattern coins. Well illustrated in colour.
Keep one by the computer to give you a realistic value of all those eBay bargains.