Love the Usborne Young Reading series of books (1-3).
I would normally review each book independently but we have had all of Series 1 (now given away) and most of Series 2 and some of Series 3 so it becomes a little burdensome to write individual reviews.
My 5 and a half year old daughter loves these books. We finished the whole of Series 1 about a year ago and now have bought about 25 of the series 2 and 15 of the series 3. She dips in and out of the series 2 and 3 books on a daily basis. She particularly enjoyed this book on electricity and we have had to read it to her many times and she has insisted that she read it to us regularly. It has to be in her top 5 of most read books so I am very happy (being an old science grad) as was looking at how to start introducing these kinds of concepts. The whole series of books are highly recommended for children just starting to read (series 1) to more advanced reading (series 2) to competent reading (series 3). The combination of ever increasing words (from series to series) and complexity mean that my child is always challenged.
We also have most of the other books published by Usborne so it's safe to say that we love this publisher!