Basic Human Anatomy and essential visual guide for artists by Roberto Osti is as good an anatomy book as you can find in the market. With simple explanations and rich visuals it's a great book for any young artist trying to learn more and sharpen their fundamentals.
The Fundamentals of drawing are very simple, Anatomy and Perspective are certainly in top 5 most valuable skills for improving. Learn some Anatomy and draw better right, sounds simple but the reality is Anatomy alone takes years if not a lifetime to master, that's why it is important to start educating your self as soon as possible and as much as possible, going to your local library and checking out some of their art books is in some ways better then clicking through the endless internet
The Stereometric Method
The Stereometric Method was devised during the Sixteenth century in a period know as the Renaissance, Italian Mannerist painter Luca Cambiaso created many sketches and compositional studies with many levels of schematization. Painter Piero della Francesca, Paolo Uccello, Albrecht Durer, and Leonardo de Vinci all used this method before starting and big work.
"The artist with a good knowledge of Anatomy will be able to create more beautiful and accurate artwork because he or she will have the means to better understand the forms of the body" -Roberto Osti
Stereometric rendering can be used for compositional purposes as well as for studying light and shadow. Because the moving figure is such a challenging subject to draw or paint, it can be of great help to subdivide the figure into various components and then reassemble them. The Stereometric approach employs boxlike shapes, it can be slow and impractical so as you progress more organic forms closer to the human body can be used.
"Once you understand how the segments of the body relate to proportionally and how they are connected you can start to create a variety of poses" -Roberto Osti
ALL text and images are taken from Roberto Osti Basic Human Anatomy