I've been playing guitar for 3 and a half years and would consider myself an accomplished intermediate player. I am pretty strong at improvising and creating and playing songs from tab. I have a bit of experience reading music for guitar (lots more for trumpet) and I sorta know my way around sheet music. But I have aspirations of attending a music school such as Berklee or Musicians Institute after finishing high school, and really want to work more on my sightreading skills with sheet music.

Would Berklee's "A Modern Method for Guitar" be useful to me to improve or is it intended more for complete beginner players?
Ibanez S320 with Dimarzio Fred + Seymour Duncan 59-> Weeping Demon Wah -> Ibanez TS-7 -> Homemade iBoost x3 -> Keeley DS-1 -> Visual Sound H2O -> MXR Ten Band -> Traynor YCV20
It is definitely worth it. I played for 2-3 years under one teacher then switched teachers and began using that book and it helped a lot. Only the first like 15 pages maybe are for the complete beginners, then it becomes more challenging.

Ibanez SZR
Cube 30
Digitech RP 250
i only got that book this year and i started playing when i was 6.
Its got a lot of great sight reading stuff, and technique improving exercises. Get it if you've got the spare cash.
But a lot of these books everyone is asking 'should i buy' are available in many different pages on the internet.
THat doesn't stop me from buying heaps and heaps of music bookss, though :P
Just to add up, I use these books now and it's working really well for me. Great book with lots of exercises. Worth all the money. And it doesn't cost that much for the three of them.

But I have no idea how Mark Levine's book will help in this matter.