My nephew is about to turn 6. He's really interested in space travel. Any suggestions for space-related books (fiction or non-fiction) suitable for a boy of this age?

try Stephen and Lucy Hawking - George and the secret key to the Universe - there'e 2 in the series

Why not check out The Wishing Book which is available now on Amazon. It is about 4 children who find a book with special powers. Following many adventures and pranks with the book, they eventually wish to go to Planet Mars and the real adventure begins. The Chief Highness of Mars hears about the book and wants it so that he can take over the whole Universe. Martian warriors, Termans (Flying creatures) and the Blattidae (giant cockroaches) attack the children in their aim to obtain the book.
The Wishing Book 2 - Return to Mars should be available later in the year and the climax - The Wishing Book 3 - Extermination, will be out in the New Year.
This is a trilogy suitable for 7 - 13 year olds, boys and girls and will keep the reader gripped until the final page.
Check out Amazon and www.authorgrahamehoward.co.uk

try this book it says age range 7-10 but should be ok i think 'The Comic Strip History Of Space
Sally Kindberg' and also 'The Greatest Intergalactic Guide to Space Ever... by the Brainwaves' i got the atlas version by the brainwaves it was fab!!

Don't know if anybody's already said it because I haven't got time to read all the comments - sorry if they have - but the two Tintin volumes Destination Moon and Explorers on the Moon have stood the test of time. Even if they have been superseded by history, the drawings and stories are so magical that it's not important. Kids (and adults) adore them!