I would not recommend Under Pressure for a first Sous Vide book. The recipes while fantastic are quite complicated and time consuming. I would go to your library and check it out before ordering.
Here is one I checked out of the library and found it very practical and it teaches as well. I got it on interlibrary loan where they do the work of finding it and having it sent to you at your local library,
https://www.amazon.com/Modernist-Cooking-Made-Easy-Authoritative/dp/0991050177/ref=as_li_ss_tl?ie=UTF8&qid=1453048097&sr=8-1&keywords=sous+vide+cookbook&linkCode=ll1&tag=anovacommunity-20&linkId=27c67be938272ccfc42a5b8e7dfe826ak