Studying smartphone development from a book. Since I don't have any real projects to showcase, is it normal to include projects I've done following the books I've read about development? Keep in mind that I changed all the names in my own version of the projects, including the look and feel, even the code to an extent.
Absolutely! You are not writing the code for a customer, so you don't need permission, especially if you learned how to do something. Created a marquee on a website? Sure, show it off! Create a beautiful, stunning, responsive website that works on mobile devices and desktop computers of all shapes and sizes? Show it off!
The point of the portfolio is to show what you can do, without directing them away from you. Check your book's copyright notice though, and make sure they allow you to use what you learned in the book for your own gain. I don't know of any books that say that, but that'd be the only "gotcha" I can think of.
My portfolio site was taken from stringing together lots of concepts I learned from a PHP and MySQL book together - Forum, calendar, contact management, email system and a chat system, all rolled into one. I got the concepts from the book, but changed it completely to match what my goal was, and it's up and live! It's on a free sub-domain, but it demonstrates the concepts, which is what a portfolio is for.
People should be able to check your portfolio and decide for themselves, "I like how this person did task X, Y and Z. I'll hire him/her. They will not likely be inspecting your code for how you accomplished a task, especially before the project has even been accepted! The point is, like a gallery, people look and contact you further if they like what they see. You should not be "creating" a portfolio for each client contact, as that will take too much of your time.
Approach this with caution. It's easy to copy something out of a book, and change images and text. It's MUCH harder if you don't really know the technology that the code from the book is utilizing, and need to materially modify the code. Clients WILL ask for modifications. The worst response you can ever give a client is, "Yes, that's my demo site. But I don't know how to modify it."