Why are there almost no mnemonics on Kanji Book yet?
First of all, if you read this post in the future, this will mostly likely not apply anymore. Hence, please move on and don't waste your time reading it.
The reason why there are almost no mnemonics yet is that until last week I told every user to not create any serious entries yet. I did this so I could focus on designing and implementing the core database. If I made a change to it, in most cases I would have had to delete every submitted mnemonic and people would have had to start from scratch. In my opinion that is a horrible experience and it should never happen. Therefore you won't find many mnemonics yet.
The good thing about the few mnemonics is that you really have to come up with your own ideas. From my own experience I can tell you that you will have the highest chance of remembering your kanji and vocabulary.
Consequently, I designed the mnemonic editor as the most prominent element in the interface so you can first and foremost focus on creating your own mnemonics. In case you can not come up with a good idea for a mnemonic, you can look below the editor where mnemonics will hopefully soon show up from other users.
To make it extremely easy to come up with a mnemonic, I intentionally designed the system in such a way that if you wanted to learn 保護者 for guardian (from JLPT N1), you would first have to know each kanji. To know a kanji, you would have to first learn the parts it consists of. For instance, let's take 護 (protect) which looks quite intimidating with its 20 strokes. To learn 護 Kanji Book will tell you to first learn its constituents 言 (word), 艹 (grass), 隹 (bird), 又 (again). This makes perfect sense because it will allow you to come up with a mnemonic like following:
A bird is walking on the grass back and forth, again and again. It seems to protect a statue with the 言 kanji on it. He seems to be the guardian of the statue.
Without this foreknowledge I would have never been able to come up with this mnemonic in less than 30 seconds. Rote memorization would have been a pain in the butt. You probably would have written flash cards and written the 護 100 times to make it stick. Make it 110 if you messed up a few strokes. I know it, because that's how I started out and made me realize that there should be an easier method. To put it in other words, Kanji Book helps you build mental "web" of known constituents and you can build upon this existing knowledge. I am already looking forward to the awesome mnemonics you will create.