Conflict of interest declaration: I'm on page 223 of this book, so I'm hardly going to give it a bad review, am I? BUT...
In the past I have been severely disappointed by "books of websites". E.g. the Insultingly Stupid Movie Physics website was great fun back when the webmaster was updating it regularly, but the book was badly thrown together and a waste of time for people who've read the website content. Even my favourite webcomics don't have the same sparkle in print. I assumed Science Ink was going to be, like a webcomic compilation, a large thin paperback with not much added value from the editor's online photo album of other people's tattoos which you can find via his blog.
So I was greatly and pleasantly surprised (I think I pre-ordered before the photo of the book was up) to find, on unwrapping this, that it is a beautifully bound hardback with clever cut-outs in the cover that allow colourful photos on the endpapers to tantalise the viewer. The Gothic blackletter used for the word "Ink" on the cover and in the photo headings is a nod to stereotypical tattoo art. The size of this book is a bit larger in the horizontal dimensions but thinner than an average hardback novel, nowhere near as big as a "coffee table" book.
In addition to a normal index, there is also an ingenious "Visual Index" of thumbnail photos so if you can't remember who or what a cool design came from, you can still look for it easily.
Content-wise, I believe there are quite a lot of photos not featured on the website (at least a lot that don't look familiar to me), in addition to all the ones that are online. A lot of the text in this book consists of the tattoo submitters' personal accounts of why they chose their particular designs. However, Zimmer has written mini-essays on the subject of a tattoo where the wearer has not given a long annotation, and his clear and elegant writing also forms chapter introductions. The hilarious Mary Roach (I've read her "Stiff" but have yet to get a hold of the others) provides a short foreword.
In summary, I would recommend this book without reservation to anyone interested in science or tattoos even if I wasn't in it!