Learn Hardcore Russian: Вечерний отдых с книгой помогает мне засыпать. - Evening rest with a book helps me fall asleep.

отдых is a masculine singular noun in the nominative case.
вечерний is an adjective modifying отдых; it matches it in gender (masc.), number (sg.), and case (nom.).
с книгой is just an additional phrase attached to the subject, not a separate subject itself.

Because the main noun отдых is singular, the verb помогает is in the 3rd person singular form:

он помогает → (вечерний) отдых помогает

Why is мне used here instead of я or меня?

мне is the dative form of я (I → to/for me).

The verb помогать normally takes a dative object: it literally means “to help to someone.”

кто? что? помогает — subject in nominative
кому? чему? помогает — person being helped, in dative

So:

Вечерний отдых с книгой (subject, nominative)
помогает (verb)
мне (indirect object, dative: “to me”)

Using я (nominative) or меня (accusative/genitive) would be ungrammatical here.

Why is с книгой in the instrumental case? Could it be с книга?

After the preposition с meaning with in the sense of “together with, accompanied by,” Russian uses the instrumental case.

Nominative: книга (book)
Instrumental: книгой (with a book)

So с книгой = “with a book.”

с книга is incorrect for this meaning. The instrumental ending -ой here is required by the preposition с.

Why is the verb помогает followed by the infinitive засыпать? Is that the normal structure?

Yes. In Russian, when помогать means “to help (someone) do something,” it’s very common to follow it with an infinitive:

помогать (кому?) делать (что?)

So here:

помогает (helps)
мне (me – dative)
засыпать (to fall asleep)

This corresponds to English “helps me (to) fall asleep”, where English often drops “to,” but Russian always keeps the infinitive form of the verb (засыпать, not a conjugated form).

Why засыпать and not заснуть or уснуть? What’s the difference?

All three are related to the idea of “falling asleep,” but they differ in aspect and nuance:

засыпать – imperfective
- Focuses on the process or repeated action: “to (be able to) fall asleep,” “to fall asleep (in general, habitually).”
- Good for talking about regular patterns or abilities: “X helps me fall asleep (whenever I go to bed).”
заснуть – perfective
- Focuses on the single result: “to fall asleep (once, to succeed in falling asleep).”
- Это помогает мне заснуть = “This helps me (finally) fall asleep (on a given night).”
уснуть – also perfective, very close to заснуть
- Often used for “finally manage to fall asleep.”

In your sentence, засыпать fits well because the statement describes a general habit: evening relaxation with a book in general helps you fall asleep regularly.

What exactly does вечерний mean here, and how is it different from вечером?

Both are connected to “evening,” but they’re different parts of speech:

вечерний – adjective: “evening (‑time)”
- вечерний отдых = “evening relaxation / relaxation in the evening.”
вечером – adverb / adverbial form: “in the evening.”
- Вечером я отдыхаю с книгой = “In the evening, I relax with a book.”

Your sentence uses a noun phrase вечерний отдых (“evening relaxation”) as the subject.
You could express a similar idea with вечером, e.g.:

Вечером отдых с книгой помогает мне засыпать.

This slightly shifts the style and focus, but both are grammatical. вечерний отдых sounds a bit more like a named routine or type of relaxation.

Why is it вечерний отдых, not вечерное отдых or something else?

The form of the adjective вечерний is determined by the noun отдых:

отдых is masculine, singular, nominative.
The adjective must agree in gender, number, and case.

Masculine nominative singular for this type of adjective ends in ‑ий:

вечерний отдых (masc. nom. sg.)
Compare:
- вечерняя прогулка (fem. nom. sg.)
- вечернее занятие (neut. nom. sg.)

So вечернее отдых is wrong because вечернее is neuter, but отдых is masculine.

Can I change the word order? For example: С книгой вечерний отдых помогает мне засыпать?

Russian word order is fairly flexible, so several variations are possible and grammatical, though the nuance shifts slightly:

Вечерний отдых с книгой помогает мне засыпать.
– Neutral, straightforward; the whole phrase “evening relaxation with a book” is presented as the subject.
С книгой вечерний отдых помогает мне засыпать.
– Slightly emphasizes с книгой (“with a book”) more, as if contrasting it with some other kind of evening rest (with TV, with the phone, etc.).
Вечерний отдых помогает мне засыпать с книгой.
– Now it sounds like you fall asleep with a book (literally holding it, maybe), which is a slightly different nuance.

All are grammatically possible; the original version is the most neutral and natural for the meaning you’re after.

What is the difference between книга and книжка? Could I say с книжкой instead?

Yes, you can say с книжкой, but there is a nuance:

книга – neutral, standard word for “book.”
книжка – diminutive; often:
- more informal,
- can sound more affectionate or casual,
- sometimes can imply a small or light book, but not always.

So:

вечерний отдых с книгой – neutral: “evening relaxation with a book.”
вечерний отдых с книжкой – a bit more cozy or informal, like “with a nice little book.”

Both are grammatically correct.

How are the words in this sentence stressed and pronounced?

Approximate stress (capital letters show the stressed syllable):

Вече́рний – ve-CHER-nee
(stress on the second syllable: веЧЕ́Рний)
о́тдых – OTD-yh
(stress on the first syllable)
с кни́гой – s KNEE-goi
(stress on кни́)
помога́ет – pa-ma-GA-yet
(stress on га́: помога́ет)
мне – one syllable, мне, unstressed but clearly pronounced
засыпа́ть – za-sy-PAT’
(stress on the last syllable: засыпа́ть)

Putting it all together in a simple approximation:
веЧЕ́рний О́тдых с КНИ́гой помога́ет мне засыпа́ть.

This kind of stress pattern is important in Russian; incorrect stress can make understanding harder, even if your grammar is correct.