I want to know what book would be best for learning how to get my technique a bit better? A lot of people say that Troy Stetina's Speed Mechanics book is one of the best for lead guitar, do you think that this is true?

Also, if any of this helps - I suck at guitar at the moment, I can do some rhythm guitar but no lead guitar.

I love thrash metal, this is the style I would like to get better at playing

I'm more interested in learning how to get better at rhythm guitar, but I still want to get better at lead guitar though. Like I would like to be able to play a few fast licks, anything that sounds kind of flash! but I really want to get my rhythm playing up to a much faster level.

And one last thing, I have RSI so I can't practise all day like i'd like to, I am limited to around 1-2 at the most hours a day