Lyme is pretty heavy. Three of my family members have it in various stages, one of them really serious. They live in rural Poland where in the forests it is more or less a given that you will contract Lyme at some point in your life. For foresters it is a better-than-even chance that they contract the disease by the time they are 30 even if they are careful, all it takes is one tick that you didn't spot and you get bitten by ticks all the time there.

Lyme disease does not 'make you stupid', but it can make you very ill. One of the possible symptoms is depression, memory loss is another so the symptoms the author describes are very much in the realm of the possible.

If you're ever bitten by a tick and you see a bulls-eye pattern around the bite get yourself to a doctor and make sure you are prescribed anti-biotics right away, do not wait (for instance until your holiday is over). I can't emphasize this enough. I don't like anti-biotics for many reasons when they are used without a good reason but Lyme disease is no picnic and the earlier you deal with it the better your chances of complete recovery. Wait too long and you're in for a world of trouble, in case you think I'm exaggerating please read the wikipedia page on Lyme disease or have a chat with my brother in law whose life is pretty much determined by Lyme in a very advanced stage.