If your book sales took a dive over the summer months, not to worry: this is often the case with indie authors. Now that the weather is edging ever-so-slowly toward fall, you should see a rise in your profits.
People read less in the summer, particularly children (this makes things difficult for YA and children's book authors). Everyone's getting outside and going on vacation, enjoying the interesting summer TV programming and working on their tan lines. It leaves little time for reading.
Books have natural peak times and slow times, and it's common for sales to become a little lethargic during the summer months. But the holiday season will soon be upon us, and that's the best time to sell books. So use this slow period to work on your marketing strategy, and make up for it.