Reddit reviews Guitarist's Guide to Scales Over Chords: The Foundation of Melodic Soloing

Start with pentatonic and blues scales, learn about chord subs, the basic 7th chords (dominant, diminshed, maj, min etc), minor scales and modes on them etc. Here's some string-specific books in my local library that i thougth good:

• http://www.berkleepress.com/catalog/product?product_id=1219764
  
  
• Waller, "Past the Print http://www.amazon.com/Mel-Past-Print-Julianna-Waller/dp/0786607564/
  
  
• Julie Lieberman wrote a few book on jazz/blues/folk styles: http://www.amazon.com/Improvising-Violin-Completely-Revised-Lieberman/dp/B0017S4802/
  
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  here's a couple good ones, non-strings specific (helps to have a piano/MIDI controller/guitar and DAW to make chord backing tracks
  
  
• Edly's Music Theory for Practical people: http://www.edly.com/mtfpp.html
  
  
• http://www.amazon.com/Harmony-Theory-Comprehensive-Musicians-Essential/dp/0793579910
  
  
• Chad Johnson, Guitarist guide to scales over chords: http://www.amazon.com/Guitarists-Chords-The-Foundation-Melodic-Soloing/dp/1423483219
  
  

This book, scales over chords has helped me alot, and the appendix is a dunk.
http://www.amazon.com/Guitarists-Chords--Foundation-Melodic-Soloing/dp/1423483219/ref=sr_1_1?s=books&ie=UTF8&qid=1346684622&sr=1-1&keywords=scales+over+chords

I don't know if someone has already told you this, but I think what you might need to make it sound less random is a technique called "chord-tone targeting". It's basically all about having awareness of the individual notes in the chord so that you can add and emphasize those notes in the solo, which ties it to the progression.

It follows that if something sounds random than you need a little more structure. This doesn't hamper your creativity, it just narrows your focus. Great musicians can make the same three notes sound amazing despite playing them over and over again.

I also just play pentatonic and sound random, so this is something I have to study and work on as well. I bought two books, Chord-Tone Soloing and Guitarist's Guide To Scales Over Chords, which I think will help me and might also help you. Happy playing!

Try books. They tend to be more focused on sequence and scope of information. While you may get some of the same info online, the manner in which a text will present it adds significant value.
here're two i've liked: http://www.amazon.com/Guitarists-Chords-The-Foundation-Melodic-Soloing/dp/1423483219/ref=pd_sim_b_4?ie=UTF8&refRID=1P4KMJPFH2RW2XY8WK6K

http://www.amazon.com/How-Write-Songs-Guitar-Revised/dp/0879309423/ref=sr_1_1?s=books&ie=UTF8&qid=1411569974&sr=1-1&keywords=write+songs+on+guitar

have fun.

I had this issue.

https://www.amazon.com/Chord-Tone-Soloing-Guitarists-Improvising/dp/0634083651/ref=sr_1_1?ie=UTF8&qid=1485559538&sr=8-1&keywords=chord+tone+soloing
https://www.amazon.com/Guitarists-Chords-Foundation-Melodic-Soloing/dp/1423483219/ref=sr_1_6?ie=UTF8&qid=1485559538&sr=8-6&keywords=chord+tone+soloing

These books (and a lot of very mindful practice) fixed that problem.