my suggestion for buying any IT book of this nature, is to do a little background research into the subject first, the very basics. Next go to your nearest large bookstore, in London for example go to Foyles or Borders. Find the relevant web authoring books, take a huge armfull of them to a sofa and flip through them all until you find one that has an attitude and a language that communicates with you. If you go through the book and all the information is going over your head then put it back on the shelf and onto the next one. look up something easy that you are familiar with doing, and see how the author explains it. look up something you would like to know how to do and see if you understand it.
I haven't ever bought any web design books, but I have for other subjects like video and networking. set aside a saturday to go shopping, the larger the bookstore you can get to the better. I have never regretted any purchases and often refer back to my books for reference, yet other books that get given to me on courses I have been sent on tend to sit on the shelf afterwards and never get opened again.