Hi!
I have a period of 2 to 3 days per page as they are 23 pages, it will be a long time, if you want before we can negotiate! I make 0 illustrations and not ready-made vectors. In my service I will make a reformulation of the concept art of the characters and scenarios, you can ask for revisions when necessary.
I have some illustrations that are similar in my portfolio to what you need, those of water and ocean: see them here:
https://www.freelancer.com/u/Decris
The value includes all illustrations, commercial license, conversion to amazon format, PDF, PNG, JPG, plus unlimited revisions!
Call me on the chat so I can do it and send you examples of my work!
Thank you!