Is it multiple choice or standard questions? Would you say they are for year 6 children or younger, such as year 3 or 4? Also, is the level of difficulty increasing with book 1 being the easiest and book 4 the hardest?
The comprehension questions are a mix of a standard format and options to choose from (a, b, c, d etc. ) but there is no answer sheet. All other questions are mainly standard format. For some questions there is no space provided to write the answers in, they would have to be written on a separate sheet of paper. In fact, when I used these books with DS, we often just talked through the questions and answers, rather than write anything down (it was much quicker that way and he still learnt what he needed.)
The comprehension passages are short but have at least 8 questions (and up to 12) to go with them, so require a reader to extract a lot of different information from a small amount of text. There are quite a lot of 'why' and 'how do we know' type of questions which are good for working on understanding and interpretation of the text. E.g. in Book 1 there is a text called 'The Dog and the Bone' and one of the questions asks, 'How do we know that the bone was a very fine one?'. In Book 4, there is an extract from 'The Glass Knife' by John Tully and one of the questions is, 'How do we know that this is a kingdom, not a republic?'.
The books are graduated in the level of difficulty, both through the series (Book 1 being the easiest) and within each book.
The 2008 edition does not stipulate the target age group, but the preface in a 1998 copy of Book 1 says: 'This book of English tests is intended for second-year pupils of Primary Schools. It can be used either for testing progress and ability, or it can serve as a textbook from which pupils can work alone or with teacher's help.' Book 2 says it's meant for 'third-year pupils', and so on. Having said that, Book 1 has some tricky general English and VR questions in it and I think it would be probably better for year 3 or bringing up to speed a year 4 child, for example. I would use Book 4 with year 5/6, depending on how good their English is and the other books anywhere in-between.
Bear in mind these books are not meant as practice for a particular style of an English test, but they help improve a child's general English skills.