I have got the first edition and really found it useful and love looking through it. When I saw an updated edition I thought it would have lots more new stuff - but not enough to justify a new edition in my opinion, so if you have the first edition thats good enough.
This is an excellent reference book encompassing information on many many potteries. There's a huge number of pictures which is invaluable. Quite apart from its usefulness, the book is an absolute pleasure to browse through.