We discovered this book series about the dog Grk and his master Tim by chance, browsing through dozens of online book stores. My son is very choosy with his books and he does not like fantasy, wizardry or magic or basically stories that are too fantastical.
The Grk books ticked all the right boxes, and not only are they well written they also managed to keep my son inspired throughout his entire year 3. The idea of a young boy and his dog solving grown up mysteries on their own to appeals any kid, and I would recommend alternating these books with something a bit more silly, such as Captain Underpants as the Grk books are fairly straight in their storytelling, although compelling.
The Grk books works for mainly boys between 7-10.