Oh boy, the things I've heard about Packt Publishing. You'd be better off publishing yourself. Their agents work on commission so they'll basically try to talk anyone into writing a book. They'll set impossible deadlines, their editors don't speak English as a first language and will often introduce errors, they ignore the corrections/suggestions of technical editors, etc. They don't do the promotion they promise. And they've been caught before "accidentally" not paying any commission on the book sales generated through a link one could add on one's own blog for readers to buy one's book. I've seen one successful author declare he sold more copies himself than through Packt and when they finally agreed to let him out of his contract due to his allegations they hadn't done what they promised, they still refused to stop selling his book themselves. He then made his book available for free on his webpage to stop them from profiting from his book.
It's a horrible, horrible outfit that's little more than a self-publishing firm that takes a large percentage of your sales and does nothing in return.