I've read that Dragonart book actually; but I'm sorry to say that I found it generally useless. I don't recommend you learn from that book even. It's got them step by step thing going on and really, you're drawing in Peffer's (If I'm correct, that's the author's name) style, not yours. Really, it's like copying someone else's work. I can actually see Peffer's style written all over your dragon drawings. Though it does offer a few hints for photoshop, I still think it's better that you experiment and develop your own technique. It's okay to read a few tutorials, but please don't base your art completely around those tutorials. I don't think you're a bad artist, but it's just that I think you're heading the wrong direction, that's all. Sorry if I was a bit cruel or anything. D8
Another problem I have with them is that I think you're attempting large full blown pieces when your skill isn't really up to it. You need to step down a bit and do smaller things. Perfect smaller projects to improve your skill so that you can take on bigger ones. Really, I only attempt the full blown thing like, once a year. And you've done 4 in less than a week, gotta give a hand to the effort. Just slow down a bit, 'kay? xD
Okay, now one more thing. I think you know where all the lines and stuff go, but don't actually know what they are. I see a bunch of lines there and it looks as though you were like 'okay, now there's a little line here at the end of the arm, just before the hand' (what I'm referring to is the ball of the ulna; of course it's just an example). However, it doesn't appear as if you know what shape the ulna is within the arm and how's it placed at different poses. Really, all I'm saying is that there's a slight observation problem here. I suggest you do more observational drawings. Y'know, do a still life of your own arm or someone else? Just to get a better understanding of anatomy and stuff. Also, you should look at anatomy diagrams. It just helps.
Oh and is your tablet broken or something? 'Cause in the last three pictures, it didn't appear as if you had pressure sensitivity or anything. Get it fixed. Your pressure and tilt sensitivity is your god from now on, okay? D<