Minä luen kirjailijan kirjaa.

I read the author's book.

Breakdown of Minä luen kirjailijan kirjaa.

• minä: I
• kirja: the book
• lukea: to read
• kirjailijan: the author's

Questions & Answers about Minä luen kirjailijan kirjaa.

Why is kirjailijan in the genitive case?

Because it marks possession: kirjailijan kirja means “the author’s book.” In Finnish, a possessor noun preceding another noun is put into the genitive singular (here kirjailija → kirjailijan).

Why is kirjaa in the partitive case instead of the nominative or accusative?

The partitive case is used for objects when the action is ongoing, incomplete, or indefinite. Saying Luen kirjailijan kirjaa implies you’re in the process of reading (not necessarily finishing) the author’s book. If you wanted to express that you read or will read the entire book, you’d use the accusative (kirjan):
Minä luen kirjailijan kirjan.

Can I omit the subject minä here? If so, why?

Yes. Finnish verb forms already encode person and number. Luen is unambiguously 1st person singular, so you can simply say
Luen kirjailijan kirjaa.
You’d include minä only for emphasis or contrast.

How would I say I am reading my book in Finnish?

You use a possessive suffix on the noun rather than a separate genitive possessor. For 1st person singular, the suffix is -ni (after consonants in partitive you get -ani):
Luen kirjaani
Here kirjaani = kirja + -ani (“my book,” partitive).

Why aren’t there articles like the or a in this sentence?

Finnish does not have definite or indefinite articles. Definiteness is inferred from context, word order, and case marking rather than separate words.

What is the base form of kirjailijan, and how is its genitive formed?

The base (nominative) form is kirjailija (“author”). To form the genitive singular, you add -n, yielding kirjailijan.

How would you express I am reading the author’s books in plural?

Use the partitive plural of kirja, which is kirjoja. The sentence becomes
Luen kirjailijan kirjoja
(“I am reading the author’s books,” implying part of one or more books, or an ongoing action).

What if I want to emphasize that it’s specifically the author’s book I’m reading—can I change the word order?

Yes, Finnish has relatively free word order. The neutral is Subject–Verb–Object (SVO), but you can front an element for emphasis. For example:
Kirjailijan kirjaa luen minä.
Here you emphasize kirjailijan kirjaa (“it’s the author’s book that I’m reading”). The meaning stays the same; only the focus shifts.