As of my experience, I would suggest you not to buy any book. It will be better if you go for Online Selenium Certification Training and QTP.
There you will have better interaction and interpretation when you learn Online. It helps you explore more knowledgeable things. You can also clarify your doubts. So it makes you more practical in-depth. Talking about Selenium, it is a portable software-testing framework for web applications. Selenium provides a record/playback tool for authoring tests without the need to learn a test scripting language. If you want to know more about Selenium I would like to mention the Selenium Tutorial. I am also giving you the link of the Selenium video tutorial which you must watch to learn more. .