Thunderbolts Reading Book Set Four is a set of 6 reading books, part of 'Thunderbolts' a series of 24 levelled reading books, covering popular non-fiction topics. The 24 low level, full-colour titles offer progression over four levels and have particular appeal to older readers. Each book features a non-fiction section together with a fully illustrated fiction story on the same topic. The books in Set Four have very limited text.