I started my daughter in these when she was 3.5. I am very pleased with her progress. We would do one letter a week with this and would play various games throughout the week to reinforce them. She finished them in 3 months and is now beginning to read. I love that these cover several skills in them and they review back over previous weeks. I would recommend them to any parent. I did work through them with her, but I imagine if your child was a little older then they could do them with little supervision. I did purchase the teaching guide and found it helpful for teaching other pre reading skills.
Utilizing these books with my 4 year old, has helped with his recognition of letters and sounds, as well as he is able to distinguish between pictures. He has applied this skilled to other areas such as toys and dinner. He now uses the book as his homework, when he comes home from daycare, which allows him to feel older becasue he is working alongside his older siblings. NOTE the books does not teach the lesson, but assist in the instruction. The teacher/parent/guardian still has to be willing to put in the time upfront to make learning successful in the end. Meaning you will need to work with your chikd for the first two or three letters After that they will be self-sufficienr in understanding the expectation on each page. Then you truly become a facilitator.
Our 4 yr old has a speech delay and has been reluctant to do schoolwork at home, especially phonetics. When this arrived, he was thrilled! I couldn't believe that he actually asked to do schoolwork. We keep each lesson short, and take more time on each sound since he has a speech delay, having him just look/point/trace the lesson first. This is helping him connect the letter to the appropriate sound, love it.