(My reply will be rambling/slightly jumbled, sorry.)
I havenāt read the series, but Iāve heard a lot of people on other forums say Shin Kanzen Master isnāt matching up to the JLPT anymore/most of the stuff in it isnāt on the test. So be careful as you go for N2. Personally, I like to use ę„ę¬čŖć®ę£® on YouTube to study grammar, but there are also other channels that teach grammar about Japanese in Japanese (ex: Meshclass ę„ę¬čŖ, å
«éę”ćæććę„ę¬čŖę室). If you canāt understand the explanations, then thatās a warning sign. There are also text websites such as JLPT Sensei and JTest4You which provide tons of example sentences for grammar points.
If you havenāt already, I recommend checking out YouTube for past JLPT audio that people upload, that will make sure you have up-to-date vocab for N2. (Either look for āJLPT N2 listeningā or use āč“č§£ā. Iāve taken and passed N5, N4, N3, and N2 and every year I listen to these audio tracks religiously + highlight and make flashcards from the free example test from JLPT Bootcamp. I think itās normal to feel overwhelmed/confused/bad at the type of vocab/grammar/kanji required for the next JLPT level, so just consider your studies as purposely eliminating your weaknesses before the big day.
The audio for the JLPT is notoriously bad and hard to understand. Not only is it boring/hard to stay engaged with, itās hard juggling listening and lightnight-fast note-taking, a lot of test rooms have bad acoustics, and you might even have a horrible thing happen like construction going on outside that day.
The gap between N2 and N3 is big (basically the training wheels should be off by now and you will only survive if youāre engaging with native content like YouTube channels, articles, manga, novels, etc). For N5-N3 for me, I would only study like crazy for 3 months before the test and passed each time. But N2 was a lot harder and I wished I had studied the entire year for it instead of only 5 months before (adding 2 extra months wasnāt enough). So if you donāt feel confident in your gap between N4 and N3, please seriously consider taking a year off from the JLPT or studying hard/taking it anyway and being prepared to take it again if you fail.
For me, I failed N2 by about 3 points for a few reasons. The main one was the girl sitting next to me stunk really bad and my nose was running like a faucet the whole time because of it. I wish I wouldāve just crammed tissues in my nose instead of wiping it like a polite person because her stench distracted me/took up so much time. If only my reading speed was faster back then, maybe her smell wouldnāt have mattered. Or if I had gotten more points in other areas, I couldāve still passed despite guessing the answers on the last 2 pages during the final seconds of the test. Anyway, I took it again a different year and actually passed, though it felt like dumb luck.
(My listening is better than my reading because I listen to a lot of native content without subtitles and use Japanese TTS like AIVOICE and VOICEPEAK every day. But my reading was horrible because I was avoiding novels and only reading manga and articles. I had to improve my mental stamina and make reading a hobby in both English AND Japanese in order to finally get myself to start reading my 2nd Japanese novel ever this year. Please donāt avoid listening or reading!)
Lastly, N2 uses keigo (ex: ~te itadaku, ~itashimasu, ~sasete itadakimasu), so pay attention while reading + document examples so you have an easier time understanding it.