Breakdown of akai hon ha medatu node wasurenikui desu.

Questions & Answers about akai hon ha medatu node wasurenikui desu.
は marks the topic, not necessarily the grammatical subject.
赤い本は… sets the red book(s) as what you’re talking about, and then you comment on it: (it) stands out, so (it’s) hard to forget.
If you used が, it would sound more like identifying which thing stands out (more focus/contrast), e.g. 赤い本が目立つ = It’s the red book that stands out.
When the hiragana は is used as the topic particle, it’s pronounced わ (wa).
So 本は is read ほんは → ほんわ (spoken as ほんわ).
In Japanese, adjectives directly modify nouns with no particle in between.
- 赤い + 本 = 赤い本 (a red book)
赤い is an い-adjective, and the plain (dictionary) form can modify a noun like this.
目立つ(めだつ) is a verb meaning to stand out / to be noticeable.
Literally it’s like to “stand” in the eyes → to be conspicuous.
In this sentence, it describes a state of the book: (it) stands out.
ので means because / since, connecting a reason to a result:
- 目立つので忘れにくい = Because it stands out, it’s hard to forget.
Compared to から:
- ので sounds a bit softer / more explanatory / more polite (often used in polite speech, formal writing, giving reasons without sounding blunt).
- から can sound more direct or more like a personal justification.
With ので, you typically attach it to the plain form of the clause:
- Verb plain: 目立つ + ので
- い-adjective plain: 高い + ので
- Noun/な-adjective: 静か + なので, 学生 + なので
You generally don’t insert です before ので in a normal clause. (There is ですので, but it’s a separate, more formal connective meaning therefore / for that reason, and it’s used differently.)
〜にくい attaches to the masu-stem of a verb to mean hard/difficult to do:
- 忘れる (to forget) → stem 忘れ → 忘れにくい = hard to forget
It describes difficulty due to circumstances (not ability/skill). Here: it’s hard to forget because it stands out.
They’re not the same:
- 忘れにくい = hard to forget (difficult for it to slip your mind; likely you won’t forget)
- 忘れられない = can’t forget (often emotionally strong: I can’t forget it, unforgettable)
This sentence is talking about memorability/noticeability, so 忘れにくい fits well.
です here is the polite sentence ending.
You can say:
- Casual: 赤い本は目立つので忘れにくい。
- Polite: 赤い本は目立つので忘れにくいです。
With い-adjectives, you can add です to make the tone polite without changing the core meaning.
It’s ambiguous (as Japanese often is). 本 can mean a book or books, depending on context.
As a general statement, it often reads like: Red books stand out, so they’re hard to forget.
If you wanted to clearly indicate “this one book,” you might add something like この赤い本は… (This red book…).