In addition to the Daily Uke, I like
Fingerstyle Solos which has a CD and starts easy (yeah, twinkle twinkle) but very soon there is a lovely Hawaiian piece and the CD in the book includes showing some mixing with instrumentation, giving you an idea of what you can do with a pickup and some mixing software. The book has one unique thing; start with "All through the night" which we all know as a folk song, then it gives another version of it later in the book, as you advance. Many styles, many genres. A very good sampler plus instruction. If you like E books, the
What Ukulele Players Want to Know is a good reference about stringing and MANY other uke topics, not on how to play but on the uke itself and much else. Highly recommended. Comes in print and ebook (Kindle)