Knitting books are an art form that get you excited about knitting each time you pick one up. Books that have good pictures, illustrations and a variety of patterns are a way to pass the time when we are not knitting. There are old stand-bys such as Barbara Walker's pattern books, the no longer hard to find Principles of Knitting by June Hiatt, and anything by Elizabeth Zimmermann. Other books include books on technique such as Alice Starmore’s Aran Knitting and color like Kaffe Fassett’s Glorious Knits.
The latest books on the knitting scene are e-books, that you can have on your phone, ipad or computer and be able to access at any time. The joy of e-books for those with e-readers is that they take up very little room in your home (which seems to be the biggest reason people don't want to buy books). E-books also make marking up the patterns easier by annotating them on the e-book. The program you use to read the book varies by the reader you own, but most of them allow annotation and the ability to highlight lines on patterns or charts.
Scanned patterns (as long as they are in the pdf format) can also be read on e-readers. Two good programs are Goodreader and iAnnotate. They both allow you to draw lines on the pattern, make pattern notes, highlight the line of the chart you are on, highlight the size of the project you are making and much more.
One more thing you do with e-books and scanned patterns is store them in the "cloud". The cloud is remote storage and processing. Companies such as DropBox, Sugar Sync, the Amazon Cloud Drive, allow you a certain amount of space for free with the option of paying for more storage if you need it. The way it works is to upload your books or scans into their storage space, which only you have access to, and then the scans or books are accessible to you whenever and where ever you have cell phone or wireless internet access.
What makes this remote storage handy is that if you see that perfect yarn at a good price you can pull up the pattern that would match it on your iPhone and you can easily find out how much yarn you need to complete the project.
The e-book and digital options are not always the least expensive option, and as always you have to decide if these features are worth paying for, but they are definitely a convenient option.