For today only (27th October) Paul Perro's Halloween picture book (Halloween Who's Whooooo!) is free. Suitable for 4-8 year olds, it's very funny and I think parents will like it too.
www.amazon.co.uk/Halloween-Whos-Whooooo-Paul-Perro-ebook/dp/B00FXA8BR6/ref=cm_cr_pr_product_top