I read @amazon reviews, the book has exercises- that's great! I've never been able to understand computer languages until I take a dig at it myself...
There are a lot of articles and books coming out on HTML5. HTML5 sure makes a programer's life easy.
I've got 2 questions for you both:
1. How many years from now will we be seeing HTML5 take over the current version.
2. How long will it take a person with decent knowledge of HTML and CSS to master HTML5 and CSS3?
Thanks Abhi for the positive comments. To answer your questions. I would start using HTML5 now. As the book explains, there are simple "hacks" to getting HTML5 section elements (specifically) to work in older browsers that do not support HTML5. As for CSS3, there are techniques for excluding certain styles from being applied if an older non-CSS3 compliant browser is detected. I know several web development shops (here in San Diego specifically) that are already building customer-paying sites using HTML5.
As for your second question...HTML5 is much easier to master IMO than HTML 4 or XHTML ever was. There are far less attributes to remember, the doctype is simpler, and with CSS3 new psuedo class selectors, once the generic makeup of your HTML is set, it's just a matter of working through the CSS. Not much tinkering needs to be done to the markup as it relates to classes and IDs.