I have  so far found this new string theory book comprehensible and clear.With a knowlege of quantum mechanics , general relativity and  some  standard undergraduate mathematics especially variational principles, group theory,topology etc.. this book looks  like  it might be the the  way into strings for thousands of  students like myself who like myself have wanted to get an actual understanding of the flavour of this highly exciting and  controvertial theoretical framework. For  self  study I think its fabulous  as  there  are  many fully worked  solution.<br><br>I think for a mathematician  or a phyics graduate this is  a better start point than Zweibach.