i need help with a issue for my ibooks

So i recently updated my iPad mini to the latest software and i when i did i noticed that one of my books for school got deleted which is my Algebra 1 book, so i go to my purchased books and it says that it's downloading so just to double check i go to my shelf and nothing there it doesn't show the cover of the book or anything, and i really need this book for school to my homework, classwork,study... etc. So if you may have a solution please tell me!!!