Books to help high functioning ASD child aged 4 with social skills?

[Foxesjumpers]

Does anyone have any recommendations for books that will help us to teach our 4 year old DS with high functioning ASD the basics of social skills? He is due to start school in a few weeks so won't be there to help him out in these situations anymore and he really does struggle. I went on Amazon and there seem to be a few books available but some are unclear as to the age groups they are aimed at.
Any advice would be well received, or any tips you might have on helping social skills too would be great!

The Blue Day Book for kids. by Bradley Trevor Greive

(Its actually more for an older primary school aged child , but a fun, great book talking about how you feel when you are 'blue' and gorgeous animal pics to match each mood and challenging situation. A Fun book to read, & giggle at the pictures with your child

Just saw your message - thank you! Just ordered it.