These are the two most recent Thor series, and they both make great starting points depending on what you're looking for.
God of Thunder is everything you could want from a classic Thor comic. The art by Esad Ribic and stories by Jason Aaron are both fitting of an epic figure of lore, and the series has already solidified itself as a classic.
Goddess of Thunder directly follows God of Thunder is the current Thor book. As you can tell, it's not the most traditional Thor story. The vibrant and incredible colors by Matt Wilson are a highlight of the series, perfect for a world of suns and rainbow bridges. This series has it's own beautiful moments, so it's great if you're looking for something different, or want a starting point closer to the current.