Sometimes this is good; it reveals strengths and weaknesses and stylistic quirks that the author can take into account the next time round. Sometimes it's just baffling ...
"The fact that it is so clearly 'written down' for children might prevent their full enjoyment."Ahem. 'Written down'? That's my actual style, thank you very much.
You don't believe me, ask a genuine child, like 14 year old Tommy who reviewed it in the Cork Evening Echo, second only to Vector and perhaps Locus as a nexus of the sfnal hive mind. Generously he gives it a 7/10, apparently deducting 3 points because "this book would really only be suitable for anyone over the age of 12 because the author uses difficult words to describe things and there is some bad language".
Sadly he doesn't cite the bad language (I'd love to know where he found it) but he does at least explain that bit about the difficult words: "I didn't like the way the author used futuristic, made-up words which he didn't explain, for example agrav."
A future in SF critique does not (yet) lie ahead of young Tommy, but give him time.