Everyman's Library Childrn's Classics covers? Any Experience?

I just received my first volume in this series, "Heidi" and would like others' opinions. While described as a hardback, the covers seem very thin and flexible to me, not even as heavy as a traditional Trade Book, do you folks feel the same? How have they held up with time? Are all Everyman's Library volumes fitted with these thin covers, or something better? At last they are sewn bindings, tat least, that's a positive. Th book is attractive, easy to read print and reasonably nice paper considering the affordable price.

Hello all,
I did receive a copy of Dracula today and now I am clear about the weight of the covers. For some reason EL decided to make the Children's series with thinner covers. But since several folks have said that the books dDO hold up well, I will continue buying. Thank you to all who offered advice.