I am going back to school to receive my Bachelors in Interactive Media and Web design. Here is a few great books I have read recently and a great starting point:
Html, XHTML, & CSS A Visual Guide 6th Edition
Amazon.com: HTML, XHTML, and CSS, Sixth Edition (9780321430847): Elizabeth Castro: Books
The Elements of User Experience: User-Centered Design for the Web
Amazon.com: The Elements of User Experience: User-Centered Design for the Web (0752064712022): Jesse James Garrett: Books
Learning Web Design: A Beginner's Guide to (X)HTML, StyleSheets, and Web Graphics
Amazon.com: Learning Web Design: A Beginner's Guide to (X)HTML, StyleSheets, and Web Graphics (9780596527525): Jennifer Niederst Robbins, Aaron Gustafson: Books
HTML Dog: The Best-Practice Guide to XHTML and CSS
http://www.amazon.com/HTML-Dog-Best-...8592552&sr=1-1
All four books are not a necessity but these are the four I suggest for a beginner to grow with. Before you even jump into designing or coding sites for clients I suggest you give The Elements of User Experience a read. All 4 of the books are part of our course reading or suggested by the Professors. I have read all four and they are all great for different reasons.