Well it let me attempt to buy the book finally but then I got an error - no book, no receipt shown in my receipts. But hey I have a pending charge for $44.99!
obviously there’s something wrong, no need to try anymore. wait until someone response here or visit the contact page: https://www.raywenderlich.com/contact
I had same issue while purchasing the book. My credit card was charged but checkout page shown me “We’re sorry, but something went wrong (500)” message. But in a few minutes, I have received an email with confirmation about book. So, now it’s available on my loot page.
sorry for the inconvenience - it was an issue with our payment provider, the purchase will go through and everything was fine, but few people saw an error 500 message, which definitely was annoying for them.