The problem with autobiography is that extraordinary people are not necessary good writers. Daniel Tammet has an extraordinary mind - he can visualise numbers, recite pi to record-breaking decimal places and learn languages with astounding ease*. This is linked to his Asperger's and also to epilepsy. 
 Although a novel human story, this does not provide much insight into how Tammet's brain works and why other brains are not like his. I expected his unique cognition would be illuminated through precise examples and that these would shed more light on cognitive psychology. Instead, this is a human interest story and can be only enjoyed as such. 
 *It is interesting that Tammet's rapid language learning is attributed to his uncanny ability to learn and apply rules but no mention is made of his lack of social inhibition, which is a huge stumbling block for adult language learners.