Thunderbolts is a series of levelled reading books covering popular non-fiction topics, with particular appeal to older readers. Each book contains a non-fiction section followed by a fiction story on the same topic. There are four sets in the series. Each set contains six books and is levelled to allow progression. Set Four increases the amount of words on each page, offering progression from the books in Set Three. The texts focus on high frequency vocabulary, with all words being phonically decodable wherever possible. Set 4 Workbook 2 accompanies Yucky Food, Polar Animals and Robots. It contains tasks to allow a degree of progression as they are used. Thunderbolts is ideal for reluctant readers aged 7 - 14 with a reading ages of 5 - 7.