Bamboo Bridge in Cu Chi

Dear all,

I have been a procreate user a couple of years. My favorite is Plein-air painting on iPad, especially Vietnam landscape. I have just published the first tutorial book on iBooks Store.

Format: iBook (54 pages)
Size: 17.3 MB
Price: FREE
Download form iBooks Store: https://itunes.apple.com/us/book/bamboo-bridge-in-cu-chi/id1223336572?mt=11

The book isn't only a tutorial painting landscape but also a collection of procreate tips.

Here is the artwork painted on iPad with procreate.

Could you please help me some ideas for improvement.
Thanks all.