Since Amazon has shut down alot of authors, including TOR books, with its embargo or whatever of Macmillan Publishers over eBook pricing, you may, like me, be looking for alternative places to buy the latest science fiction.
I have found a few science fiction specialty stores on the web. While do ship and they have presences on the web, their sites do not tend to be great for browsing for new titles.
These specialists in science fiction have a great advantage over Amazon in that they have deep knowledge of the literature and they will help you find what you're looking for, and can recommend more authors you may not know about.
If you're looking for new science fiction and fantasy as eBooks, try the Book Cafe. This an an author run site, no middle personages to get between you and your books.
Minneapolis bookstore Uncle Hugo's has a large selection. They print newsletters which list their incoming titles, so look for that on the sidebar as "browse new books".
The Dark Carnival Bookstore in Berkeley, CA is packed with science and fantasy new and old. Their site lists featured new items, and the store owners will certainly let you know if they have what you're looking for that isn't listed. They have adult, YA and children's titles, so ask if you don't see what you're looking for. Click on the Recommended link in the sidebar.
Happy reading. If you have online science fiction bookstore recommendations I didn't find, let me know, I'll add them to the list!