Yes, the standard English pronunciation of 'Adam' is /'ædəm/. The stress is on the first syllable, while the second syllable is a schwa /ə/. Any English-speaking person seeing this name written down would always pronounce it this way. However, there are many languages in the world where 'Adam' is pronounced with the stress on the second syllable The pronunciation in the Oxford Reading Tree is unusual in an English-speaking context. However, I am sure that this is deliberate - it is not a mistake. This pronunciation is used because the writers are trying hard to be multicultural. Looking at the picture of the boy called Adam in the O.U.P. illustrations, I can see that he has dark skin, so I presume that he is intended to be a character of non-white heritage. This is why the producers instructed the reader to say 'Adam' in a 'non-English' way, with a stress pattern consistent with the pronunciation of a language other than English.

British pronunciation versus American pronunciation is probably the difference.