Book lol

First off, kudos to you for choosing a dynamic angle to portray this woman in. Most people don't attempt it because it is very difficult. Anyways, The first thing I notice is that her face is a little off. The human head is round in shape and often drawing guide lines for the face could help fix this problem. Instead of a straight line down they should curve from her lower brow bone done to where to nose would be then curve back up. That would raise her right eye up a little higher thus giving her face more depth and more realistic. Also, I would suggest adding more eyelashes to the right eye but on the left portion of her eye, seeing as the most eyelashes are from the outer portion.

If you wanted to make those eyes work with that angle you would have to make the nose, lips, and jaw more angled downwards to increase the angle of her looking down. Also, the bridge of the nose is off, it usually slightly indents prior to the actually flesh of the nose. Also, I see a slightly darker spot for the nostril, but if she was looking down at that angle you wouldn't be able to see it.

As for the lips, the same rule applies from the eyes. Also her facial features should line up more, i.e. her lower lip and upper lip seem to be crooked, maybe it's the way she's smiling?

I really like the implied lines of her collar bone. And how you shaded her neck area. I feel that a line defining her neck would add more impact to this picture.

I really like the background, it's simple yet effective. Allowing the viewer to focus on the girl and her grin. I also like the book. But I felt it could use some more shading in certain areas, depending on your light source.

Overall, well done, and please don't take anything personal or offensively. I mean well and encourage you to continue creating artwork that depicts difficult angles. It's those ones that really can help improve art quality and technique. : ) Have a good day/night.