Learn Hardcore Dutch: Dit boek is niet geschikt voor kinderen, want het heeft veel moeilijke woorden. - This book is not suitable for children, because it has many difficult words.

In Dutch, geen negates nouns, for example Ik heb geen boek (“I don’t have a book”). To negate an adjective or an entire sentence, you use niet. Since geschikt is an adjective here (“suitable”), you say niet geschikt rather than geen geschikt.

Why is the preposition voor used in voor kinderen?

The verb/adjective geschikt (“suitable”) is always followed by voor when indicating the target or recipient. So “suitable for children” becomes geschikt voor kinderen. You could think of it like English “for.”

What is the difference between want and omdat, and why is want used here?

Both want and omdat mean “because,” but they behave differently:

want is a coordinating conjunction (it joins two main clauses and keeps normal word order).
omdat is a subordinating conjunction (it creates a subordinate clause and pushes the verb to the end).
In your sentence, want keeps a simple main‐clause structure: …want het heeft…. If you used omdat, you’d have to say …omdat het veel moeilijke woorden heeft.

Why is the verb order want het heeft and not want heeft het?

Because want is coordinating, it does not change the usual Dutch verb‐second (V2) order. The subject het comes before the verb heeft, just like in the first clause Dit boek is….

Is the comma before want mandatory and what is its purpose?

The comma before want separates two independent clauses and helps readability. In short sentences it’s not strictly mandatory, but Dutch style guides generally recommend using it to avoid confusion.

In het heeft veel moeilijke woorden, what does that first het refer to and why not hij?

The pronoun het refers back to het boek. Dutch nouns have grammatical gender (common or neuter). Boek is neuter, so its pronoun is het, not hij (which is used for common‐gender nouns like de man or de tafel).

Why is the adjective moeilijk inflected as moeilijke before woorden?

Adjectives get an -e ending when they stand directly before a noun that is either:

singular with de, or
plural with de/het, or
indefinite (no article) and plural.
Here woorden is plural and indefinite, so moeilijk becomes moeilijke woorden.

Could you use a different verb instead of heeft, like bevat or staat?

Yes. Bevat (“contains”) is a good alternative:
Dit boek is niet geschikt voor kinderen, want het bevat veel moeilijke woorden.
Staat (“says”) wouldn’t fit here unless you change the meaning:
…want er staan veel moeilijke woorden in.
That literally means “because there are a lot of difficult words in it.”

Could we say Dit boek is ongeschikt voor kinderen instead of niet geschikt?

Yes, ongeschikt means “unsuitable.” Both are correct:

niet geschikt = “not suitable,” literally negating geschikt
ongeschikt = “unsuitable,” one word
Stylistically they’re interchangeable here.