I have to disagree with you there, Max. Yes, those lines are thick and ordinarily could be considered too much but it is obvious that this is the stylistic choice that was made for the map. As Felwynn says, it is a cartoony style (makes me think of certain Nickelodeon shows or the Clerks cartoon that was mercifully cut short for being absolute garbage). I do think, however, that the thick lines coupled with the quite dark grey background may be a little overpowering. Maybe if the grey background was toned down a little? That's just an opinion though.

I really like it.