I have read many times the second and third editions, and having them at your bookshelf makes you ask yourself if buying the fourth edition would be worth.
But comming from Martin, that question has a clear answer: GET IT!.
I was waiting for the Spanish translation but could not wait. I have gone through it and it's clearly not disapointing.
A few reasons for previous editions owners:
* Martin gives this time clear directions on what he does. Always preceed by a warning "This is what I do, may be it's not the standard way, but it's my way". And clearly many (or all) suggestions make sense.
* The book brings Alex Mustard's work. It looks their collaboration in organizing trips, and wetpixel's posts it's not the only thing they share.
* There are clearer directions on how to improve your pictures on your computer.
For first time potential readers, some points:
* If you have not read any book from Martin, then you are really new in UW Photography. Get It!
* Read it
* Re-Read it
* Re-Read it, and wait until next Martin's edition.
Enjoy it as much as I've done!
Nacho