I'm intermediate in Japanese (conversational + able to read at an N2 level, albeit slowly), and my first response to anyone who says they "learned X kanji" is "how many words do you know?"
There's probably some value to learning the meaning of individual kanji in isolation, but it's very limited (especially in Japanese). Most words have only tenuous relation to the meanings of their individual kanji, and "learning kanji" is kind of a crutch for beginners to pretend that they're making rapid progress.
I suppose from that perspective, "learning X kanji in Y days" is a useful meme, because it pushes people to quickly move on from the approach. But that said, for most learners, it's much better to simply start learning words.
The RTK/RTH method is nothing like learning an alphabet: at no point in my education did we sit down for weeks and "learn the meaning" of A, B, C...etc. For phonetic alphabets like hiragana and katakana and roman and hangul, it's absolutely worthwhile to memorize the shapes of the characters, because there's a small set of them, and once you know them, you can convert written words to sounds. With RTK, that's not true at all.
An adult of average intelligence can learn to read kana in a week. That's time well-spent. Spending months memorizing the "meanings" of kanji is a whole other process, of dubious value.
"Learning kanji and vocabulary at the same time isn't a big deal."
This is true, and is the way that Japanese children learn the language: you learn a character, along with some words that contain the character. To the extent that individual kanji have meanings, you learn them in context.
"I don't know why you are saying "move on" because as I said, it is one more thing you have in your toolbox."
Most people who do RTK don't do it this way -- they do things like the OP, and try to "memorize X kanji in Y days". I think that's largely a waste of time.
After RTK, I created ways to mentally breakdown and identify the characters. Then, suddenly, I was able to learn words much faster too - instead of struggling with “well this one has this curve here and then it points there and it means that”, reading became automatic, and I could focus on the word itself.
The right part in this case signifies a similar pronunciation:
汁 (zhi)
十 (shi)
This is a typical setup in Chinese character, part of it relates to the meaning, the other relates to the pronunciation.
As an example: 果裹猓粿蜾 are all pronounced identically - guǒ - but mean “fruit, package, monkey, rice cake, wasp” respectively. The radicals are more useful: in the last three, you have the “animal” radical (monkey), one of the “food” radicals (rice cake), and the “bug” radical (wasp).
> 我把身子用毯子裹上。
> Wǒ bǎ shēnzi yòng tǎnzi guǒshàng.
> I wrapped myself up in a blanket.
This last example shows that just like in English, words that are pronounced the same in Chinese can be distinguished by part-of-speech. You'd rarely confuse "red" the color and "read" (past tense), even though they're pronounced the same, because the first is an adjective and the second a verb (except in the old pun "What's black and white and read all over?", where you think "read" is actually "red" due to the grammatical structure of the sentence).
This is a pretty good explanation of how Chinese characters work, explained via English words: https://www.zompist.com/yingzi/yingzi.htm
(The other three "guǒ" characters are quite rare, so may be literary-only.)
This is a riddle not a pun.
I focused entirely on how to memorize the characters and how to remember to write them based on the keyword + primitive.
That's how chinese characters became a lingua franca between diplomats in ancient East Asia. They didn't have to speak each others languages, they just had to know the same character and communicate their ideas effectively enough on paper.
It was an absolute grind. But it worked.
I'm also finding that my biggest barrier is pronunciation. I'll see the character and immediately know the meaning because I created a good mnemonic. But getting the pinyin right is harder (shuffling matters here too!).
Lastly, as dak pointed out, this book doesn't teach you how to read -- or speak -- but that doesn't mean it isn't useful. It is helping me to read, but that's because this isn't the only tool I use. In Chinese, words are really compound words. For example, 熊猫 means panda. But 熊 means bear and 猫 means cat. This makes these unbounded morphemes, which is different than what we do in the Indo-European languages. And Chinese is composed of radicals that make things harder. 果汁 is juice, but 汁 is juice. The three ticks on the left are the symbol for water but 十 means 10. The book focuses on the latter cases but you'd be very confused if you read about the bear cats of China. And these are just the simple examples. I'm sure others will write some more fun ones below (I'm a real novice at Chinese).