Learn Hardcore Chinese: Tā de lǐxiǎng shì dāng zuòjiā, suǒyǐ hěn xǐhuan dú xiǎoshuō. - Her ideal is to be a writer, so she really likes reading novels.

Without 的, 她理想 sounds wrong in standard Mandarin; you almost always need 的 between a pronoun and a regular noun like this.
(There are some fixed expressions without 的 like 我妈, 他哥, mostly with close family terms, but 理想 is not one of those.)

What exactly does 理想 (lǐxiǎng) mean? How is it different from 梦想 (mèngxiǎng) or 梦想当作家?

理想 means an ideal / aspiration / goal you seriously hope to realize. It often sounds a bit more rational or realistic.
梦想 literally has dream in it and can feel more emotional or romantic, sometimes less realistic.

她的理想是当作家 = Her aspiration/goal is to be a writer.
她的梦想是当作家 = Her dream is to be a writer (more emotional, story-like).

Both are correct; the nuance is mostly about how “serious vs dreamy” you want to sound.

Why do we have both 是 and 当 in 她的理想是当作家? Isn’t one “to be” enough?

The basic structure is:

A 是 B → 她的理想是 … = Her ideal is …

Here, B is the phrase 当作家:

当 roughly means to serve as / to work as / to be (in a role).
作家 = writer.

So literally: Her ideal is (to) work as a writer.
是 links 理想 and the predicate; 当 shows that the predicate is a role or profession.

What is the difference between 当作家, 做作家, and 成为作家?

All three can be used, but with slightly different feels:

当作家 – very common; focuses on taking on the role / working as a writer (career/position).
做作家 – also possible; 做 is a general “do/be” verb. Slightly more casual in this context.
成为作家 – literally become a writer; emphasizes the process of becoming, often sounds a bit more formal/literary.

In this sentence, 她的理想是当作家 is very natural conversational Chinese.
她的理想是成为作家 is also correct but feels a bit more formal or written.

Could we say 她的理想是作家 without 当 or 成为?

Usually you wouldn’t.
理想 is something you do / become, so we expect a verb or verb-like element after 是:

Natural: 她的理想是当作家 / 成为作家 / 做一名作家。
Unnatural: 她的理想是作家。 (It sounds like something is missing.)

So you normally add 当 / 做 / 成为 to make it grammatically and semantically complete.

Why is there no 她 after 所以? In English we say “so she really likes…”.

In Chinese, if two clauses share the same subject, the subject of the second clause is often omitted:

她的理想是当作家，所以很喜欢读小说。
→ “Her ideal is to be a writer, so (she) really likes reading novels.”

You can say 所以她很喜欢读小说, and that is also correct.
Dropping the second 她 is just more concise and very common in spoken and written Chinese when the subject is clear from context.

Does 很 in 很喜欢 really mean “very”? Could we just say 喜欢读小说?

很 before adjectives (and some verbs like 喜欢) often serves two roles:

A neutral linker: it makes the sentence sound complete and natural.
A mild intensifier: like “quite / really” rather than “extremely”.

In everyday speech, 她很喜欢读小说 can mean either:

simply “she likes reading novels” (with little emphasis), or
“she really / quite likes reading novels” (if stressed in speech).

You can say 她喜欢读小说, and it’s grammatically correct; it may sound a bit more bare or matter-of-fact, especially in isolation. Using 很 is more typical and natural.

Why is it 喜欢读小说 and not just 喜欢小说?

Both are possible, but they don’t emphasize exactly the same thing:

喜欢小说 – like novels (as a type of thing).
喜欢读小说 – like reading novels (the activity).

In English we often blur this difference, but in Chinese adding 读 makes it explicit that the activity of reading is what she enjoys, not just the genre abstractly.
Given the sentence’s focus on her being a future writer, emphasizing the reading activity makes good sense.

What is the difference between 读小说 and 看小说?

Both can mean “read novels”:

读小说 – focuses on the act of reading (more bookish/formal).
看小说 – more colloquial; 看 is a general word for look at / watch / read.

In daily speech, many people say 看小说 more often.
读小说 is absolutely correct and sounds a bit more “proper” or slightly formal, which fits well in a written example sentence.

How does 所以 work in this sentence? Is the structure like because… so…?

Here the pattern is:

Reason (clause 1)，所以 Result (clause 2)。
- 她的理想是当作家，所以很喜欢读小说。

Literally: Her ideal is to be a writer, so (she) likes reading novels very much.

If you include 因为, the common pattern is:

因为 Reason，所以 Result。
- 因为她的理想是当作家，所以很喜欢读小说。

In everyday speech people often use just one of them:

因为… (with no 所以) …
or …，所以… (with no 因为)

This sentence uses only 所以, which is very natural.

Where should 很 go in the sentence? Could we put it somewhere else, like 喜欢很读小说?

很 is an adverb that comes directly before the adjective or verb it modifies:

Correct: 很喜欢 – really like
Incorrect: 喜欢很读小说, 喜欢读很小说 – both ungrammatical

So the correct word order is:

所以很喜欢读小说。
Adverb (很) → verb (喜欢) → object (读小说 as verb-object phrase).

Chinese word order is quite strict with adverbs: they normally appear before the main verb, not randomly inside the verb-object phrase.

There is no tense marker. How do we know if this is present, past, or future?

Chinese usually doesn’t mark tense the way English does.
她的理想是当作家，所以很喜欢读小说。 is neutral in time; context decides whether we read it as:

“Her ideal is to be a writer, so she really likes reading novels.” (present)
“Her ideal was to be a writer, so she really liked reading novels.” (past)

If you need to be explicit, you add time words:

从小，她的理想就是当作家，所以一直很喜欢读小说。
From childhood, her ideal has been to be a writer, so she has always liked reading novels.
将来，她的理想是当作家。
In the future, her ideal is to be a writer.

Without those, the sentence is interpreted by default as a general present statement.