Yes, thinking of は as a topic marker is a good stepping stone to learning the purpose that は really serves in the Japanese language. I have also heard that が is an emphasizer. In truth, depending on the usage, they are both types of emphasizers because they call attention to the sentence subject or conversation topic. How you think about them depends on how far you are in your study of the Japanese language. If you have not yet had an epiphany about their meanings then I would say you should continue to think of は as a topic marker. I will try to elaborate though.
When you use は, you are calling into existence the notion of something - it may be a sentence subject or conversation topic - and subsequent statements and perhaps even an entire conversation will revolve around that thing. In this sense, は is both a sentence subject and conversation topic marker.
Getting more complex, as it tends to be in real Japanese conversations, you can use multiple instances of は or start invoking が to add emphasis and contrast.
This probably makes little-to-no sense without an example, so check this out and assume this is a full conversation from start to end - if it helps, think like two friends walked into a pet shop and started talking. I don't think you would ever find this explanation in a book, and I am not going to explain every bit of grammar in detail, but I think this should help.
Person A: 犬は可愛いです。
(ひらがな: いぬ は かわいい です。)
(Romaji: inu ha kawaii desu.)
(English: Dogs are cute.)
- Here, は is both a conversation topic and sentence subject marker. Dogs are the topic in the conversation, and dogs are also the subject in this sentence.
Person B: いや、私は猫が可愛いと思います。
(ひらがな: いや、わたし は ねこ が かわいい と おもいます。)
(Romaji: iya, watashi ha neko ga kawaii to omoimasu.)
(English: Nah, I think cats are cute.)
- Person B disagrees with Person A. To do this, they set the sentence subject to themselves (私は) and they are stating something that contrasts with Person A so they use が to do that (猫が). The topic of the conversation remains dogs, but with this sentence cats are also added to the list of conversation topics. If you didn't say it like this and randomly start talking about cats, then you would be considered rude for starting a different conversation.
Person A: でも、私は、犬は一番可愛いと思います。猫が可愛いと感じたことはありません。
(ひらがな: でも、わたし は、いぬ は いちばん かわいい と おもいます。 ねこ が かわいい と かんじた こと は ありません。)
(Romaji: demo, watashi ha, inu ha ichiban kawaii to omoimasu. neko ga kawaii to kanjita koto ha arimasen.)
(English: But I think dogs are the cutest. I never felt that cats were cute.)
- Person A is going to acknowledge Person B's opinion but be a little obstinate. To show that, they start by saying でも, then set the sentence subject back to themselves (私は) and then refer to the conversation topic of dogs again (犬は) and share the opinion that dogs are the cutest (一番可愛いと思います). They even go so far as to clearly state their opinion of cats (猫が) in contrast to their opinion of dogs by stating they never felt cats were cute (可愛いと感じたことはありません)
As a side note, in Japanese culture, in addition to it being rude to start new conversations without continuing one started by someone else, Person A and Person B would not outwardly disagree with each other this much unless they were close friends. Otherwise they probably wouldn't become closer friends after this exchange. We don't care about Person A and Person B's relationships here, though. We just want to look at different usages of は and が as well as the interplay between the two.
If I were to give some advice, it would be that in Japanese you have "conversation topics" and "sentence subjects". は and が are used to identify both, which is confusing. Try to identify and distinguish between the two. In some cases は and が can even mark the sentence subject and conversation topic at the same time, such as in the first sentence by Person A above.