These two Excel Services books are out (or will very soon be). I decided to use this space to shamelessly promote them! :)
The first book is called "Beginning Excel Services" and is written by Liviu, Eran and Craig. I have been working with Liviu for about 8 years now and with Eran for close to 12 years. I have worked with Craig for about 3-4 years on Excel Services. All three are incredibly professional and this book should be the corner-stone for anybody wanting to deploy Excel Services. As a bonus, this book will probably become a collectors item in the next few years as this is the only known picture of Liviu (left-most in the picture) where he's actually smiling.
The second book ("Professional Excel Services") is by yours truely (yes, that's my ugly mug on the cover - I told Wrox that having my picture on the cover will hurt sales, but they didnt listen),