I wish I could recommend a book of anatomy for artists but I can't. There are a few passable books on the subject but no great ones. Some of the manga books are good for cartoony girls' anatomy, some of the older books are good for illustration reference, but no book I know of discusses the human body the way it really is.
Where a lot of books fail is that they rely on simplified muscle charts like the one above. Nobody has a split calf like the one in the drawing above. I'm sure the drawing is accurate but in real life some additional muscles, ligaments or fat must cover the two parts of the calf and make them seem like one.
Look at the drawing of the sternomastoid muscles on the left, above. According to the drawing charts they form a big "V" in the neck. You can only see half of them here but you know what I mean.
Now look at the photo on the right (above). The "V" is clear enough when the neck is normal but when it's strained as it is in the picture, or the face grimaces, the V becomes an "A." That's because muscles the drawing doesn't show cover the sternomastoid and they also have an influence on the way the neck looks. The muscle charts are incomplete. They leave out muscles just to have a tidy drawing.
Before I leave the subject here's a couple of photos (above) to prove that most people have long torsos in relation to their legs. You could almost say that long legs are an invention of artists.
My guess is that less than 20% of adults have long legs. A lot of women who appear to have long legs seem that way because they're wearing heels. Or maybe they have long legs but even longer torsos.
Do you disagree?