Research conducted by Ipsos Mori on behalf of the company showed 46% of parents used the books to entertain children during the holidays - making them more popular than any other products listed such as games consoles or portable DVDs.
Recognising that big and bulky books are less practical for this use, Egmont has decided that this summer its annuals will be A5 sized with a hardback cover.
Egmont UK group sales director Gillian Laskier said: "We are delighted with the positive response from retailers and are excited to be leading the way with this new annual format."
Egmont publishes annuals for children's characters such as Thomas & Friends, Ben 10, Disney Princess and SpongeBob SquarePants priced at £5.99.
Egmont moves summer annuals to handy A5 format
Children's publisher Egmont has changed the format of its annuals after research showed they were often used to keep children occupied during long journeys.
