What you should use is what is best suited to your learning style. If you find it easy to remember things by associating abstract imagery with vocabulary as a mnemonic, then "Remembering the Kanji" might be a good book for you. It's interesting the kinds of associations it makes with each radical of each Kanji type, but sometimes the mnemonic given differs from the actual meaning of the radical and might become confusing later. However, that depends on if you plan to learn a Kanji's radical or not. You will learn how to write the Kanji and you will be able to memorize the form well, but you wont really be taught how to use them in context; In this way, Remembering the Kanji might slow down the learning process for you.
For me, I prefer to learn all Kanji in context. I will read a text that is suited for my level and if I come across a word I am unfamiliar with, I will write it down for later. Afterward, I will use the list of words I wrote down and write my own sentences (maybe 3 or 4 each) using the new vocabulary and ask a native to make sure I correctly understood the meaning and usage of the word. This way, you will learn Kanji in a more natural way in combination with others, so that it becomes accessible immediately. This is how I learn. It may or may not work for you, but that will be for you to discover.