Learn Hardcore German: Früher nutzte niemand diesen Ratgeber, aber jetzt ist er sehr beliebt. - Nobody used this guide in the past, but now it is very popular.

Früher is an adverb meaning “formerly” or “in the past.” In German main clauses, the finite verb must occupy the second position (the V2 rule). By putting Früher in the first position, the speaker topicalizes “formerly” and places the verb nutzte immediately after it. The structure is:
1st slot (adverb) – finite verb – rest of sentence.

Why is the verb nutzte in the simple past (Präteritum) here instead of the present perfect (Perfekt)?

In written German, especially in narrative or descriptive contexts, events that happened in the past are often told using the Präteritum. nutzen is a weak (regular) verb, so its Präteritum form is nutzte. In spoken German you might hear “hat niemand diesen Ratgeber genutzt,” but in writing or formal contexts nutzte is perfectly normal.

How do we form the Präteritum of nutzen, and is it a regular or irregular verb?

nutzen is a regular (weak) verb. To form its Präteritum, you take the stem nutz- and add the ending -te for the 3rd person singular:
ich nutzte
du nutztest
er/sie/es nutzte
…

Why is the subject niemand not declined as niemanden here?

niemand means “nobody” and is in the nominative case because it’s the subject of nutzte. In German, niemand has no ending in the nominative singular. If you used it as a direct object, you would say niemanden (accusative).

Why is the direct object diesen Ratgeber instead of dieser Ratgeber?

Ratgeber is a masculine noun. In the accusative singular, the demonstrative pronoun dieser takes the ending -en, becoming diesen. So:
Nom. der Ratgeber
Akk. diesen Ratgeber

What exactly does Ratgeber mean in English?

Ratgeber literally means “adviser,” but in this context it usually refers to a “guide” or “advice book.” So the sentence says “nobody used this guide/advice book before.”

How does the coordinating conjunction aber affect word order in the second clause?

aber is a coordinating conjunction, so it does not send the verb to the end (unlike subordinating conjunctions such as weil). The new clause after aber is a full main clause with its own V2 order:
1st slot – finite verb – rest.
Here, jetzt occupies the first slot, so ist remains second.

Why is jetzt placed before the verb ist, and could you place it elsewhere?

Placing jetzt in the first slot emphasizes “now.” You could also say aber er ist jetzt sehr beliebt, where er is first and jetzt follows the verb. Both are grammatically correct, but aber jetzt ist er sehr beliebt highlights the contrast in time.

Why is beliebt not inflected with an ending like beliebter?

Here beliebt is a predicative adjective following the linking verb ist. Predicative adjectives in German remain in their base form without any case endings. If you used an attributive adjective directly before a noun, you would inflect it (e.g. ein beliebter Ratgeber).