Learn Hardcore German: Die Figur in diesem Roman ist interessant. - The character in this novel is interesting.

A fictional person in a book, film, play, etc. – a character
- Die Figur in diesem Roman = the character in this novel
A physical figure or body shape – figure
- Sie hat eine schöne Figur. = She has a nice figure.

Which meaning is correct depends on context. Because Roman means novel, Figur here clearly refers to a literary character.

Why is the article die used with Figur? How do I know Figur is feminine?

Figur is grammatically feminine in German, so it takes the article die in the nominative singular: die Figur.

Unfortunately, grammatical gender is mostly something you have to memorize with each noun. There are some patterns, but they are not perfect. For Figur:

Dictionary entries normally show the gender: die Figur.
When you learn a new noun, always learn it together with its article and plural:
- die Figur, die Figuren.

So the subject here is die Figur, and that is why the sentence starts with Die Figur ….

Why is it in diesem Roman and not in diesen Roman or in dieser Roman?

The form diesem is dative singular masculine, and it is required because of two things:

Roman is masculine: der Roman.
The preposition in is being used with the dative here, because it describes location (where something is), not movement.

in can take:

dative: for location (where?) – in diesem Roman = in this novel
accusative: for movement (into where?) – in diesen Roman would only work in a motion context like into this novel (which is unusual literally).

So for a static location, you need dative:

masculine dative: in dem Roman or in diesem Roman.

What case is diesem Roman, and how is diesem formed from dieser?

diesem Roman is in the dative singular masculine.

The base word is dieser (this). It changes form depending on gender, number, and case. For the singular forms:

Masculine:
- Nominative: dieser Roman (this novel – subject)
- Accusative: diesen Roman (this novel – object)
- Dative: diesem Roman (to/at/in this novel)
Feminine:
- Nominative/Accusative: diese Figur
- Dative: dieser Figur
Neuter:
- Nominative/Accusative: dieses Buch
- Dative: diesem Buch

So diesem here matches the gender (masculine), number (singular), and case (dative) of Roman.

Could I also say in dem Roman instead of in diesem Roman? Is there a difference?

Yes, you can say in dem Roman; it is grammatically correct.

Differences:

in diesem Roman = in this novel (points to a specific novel near in context, like this one we are talking about).
in dem Roman = in the novel (also specific, but just the definite article, not the demonstrative this).

Also, in everyday speech and writing, in dem is often contracted to im:

in dem Roman → im Roman

So you might also see:
Die Figur im Roman ist interessant. = The character in the novel is interesting.

Why are Figur and Roman capitalized?

In German, all nouns are capitalized, regardless of where they appear in the sentence.

Figur is a noun → capitalized.
Roman is a noun → capitalized.
diesem and interessant are not nouns, so they are not capitalized.

This is a standard rule of German spelling and one of the visible differences from English, where only proper nouns and sentence starts are capitalized.

Why is it interessant and not interessante? I thought adjectives take endings in German.

Adjectives take endings when they directly modify a noun (attributive position), but not when they come after a verb like sein (to be) in a predicate position.

Compare:

Attributive (with ending):
- Die interessante Figur = the interesting character
  The adjective stands directly before the noun, so it needs an ending (-e here).
Predicative (no ending):
- Die Figur ist interessant. = The character is interesting.
  The adjective comes after ist, so it stays in its basic form interessant.

In your sentence, interessant is a predicate adjective, so it does not take an ending.

Could I change the word order, for example: Die Figur ist in diesem Roman interessant? Does that change the meaning?

Yes, Die Figur ist in diesem Roman interessant is grammatically correct. The basic meaning stays the same, but there is a small difference in emphasis:

Die Figur in diesem Roman ist interessant.
- Slightly stronger focus on which figure is meant: the character in this novel (not in some other context).
Die Figur ist in diesem Roman interessant.
- Suggests that this character is interesting specifically in this novel (possibly implying that the same figure might appear elsewhere and not be as interesting).

Both sentences are fine; German word order is flexible for adverbial phrases like in diesem Roman, but it can subtly shift the focus.

How do I pronounce Die Figur in diesem Roman ist interessant?

A simple pronunciation guide (stressed syllables in caps):

Die – like English dee
Figur – fee-GOOR (stress on gur; the g is hard, as in go)
in – like English in
diesem – DEE-zem (stress on die)
Roman – ro-MAHN (stress on man, with a broad a as in Italian pasta)
ist – like English ist in fist without f
interessant – in-te-re-SSANT (stress on the last syllable; final t is pronounced)

Spoken slowly:
Dee fee-GOOR in DEE-zem ro-MAHN ist in-te-re-SSANT.

How would I say: The characters in this novel are interesting?

You would use the plural forms:

Die Figuren in diesem Roman sind interessant.

Changes from the singular sentence:

Figur → Figuren (plural of die Figur)
ist (3rd person singular) → sind (3rd person plural)
in diesem Roman stays the same (still masculine dative singular; the novel is still one)
interessant stays the same in predicate position (no plural ending).

So:

Singular: Die Figur in diesem Roman ist interessant.
Plural: Die Figuren in diesem Roman sind interessant.