Hello! There are two Minna levels, "beginner" and "lower intermediate".
Each level comprises two main textbooks, so both levels require working through four textbooks in all.
My understanding is that completion of the beginner series would be the equivalent of JLPT level 4 knowledge. Completion of the Minna lower intermediate series would be equivalent to JLPT 3 verging on 2. You can google Japanese Language Proficiency Test to find out what the various levels are supposed to mean.
My layman's opinion is that if you were to complete the Minna beginner series, you would be comfortable with some basic and useful Japanese constructions, and you'd be acquainted with some necessary vocabulary, but you would in no way be considered fluent or highly functional.
I think on the whole the Minna beginner series is well designed, and can work for independent learners. As with all learning systems, however, the benefit one derives is proportional to the effort one puts in.
in the preface of the book translation and grammatical notes it says that the focus is conversation.if i finish the series will i understand written japanese well or i'll be more skilled in conversational japanese rather than written?
I have to say I was not aware that Minna's stated focus was on conversation. My understanding had been that the series supported three foundations of language acquisition: reading, writing, and listening. A small part of every Minna lesson also involves speaking, but to do the exercise justice, a group environment is necessary, which is something an independent learner probably won't have access to. In other words, my suggestion is that an independent learner will have seek out another method to practice conversation.
Reading, writing, and listening skills should, however, all be equally developed if one follows the Minna course faithfully.
I didn't use minna no nihongo (I was too GENKI), but once you've cleared the intermediate learning materials, there are a lot of materials you can use to improve your Japanese. I have a box of various textbooks and back home, the only ones I remember fondly are "Cultural Episodes" by Japan Times (a series of increasingly challenging essays, the cover in the link is different from the edition I have but from the reviews I think it's the same book), 日本人の知らない日本語 (super interesting and great reading practice) and How to Sound Intelligent in Japanese, which I obviously never finished reading (HAH self-own), but found entertaining because it mostly talked about the theories of Japanese, which I enjoy.
I have some materials specific to studying and even N1 textbooks, and honestly I've never spent much time with them because I'm not a very motivated self studier. I've also never taken on any of the JLPT exams, but I've taken a few practice tests to check my level, and though I'd crush the N2 I know I'd need to seriously study to pass the N1; the difference between N2 and N1 is pretty huge. If you're really goal-oriented it's fine, but why not clear your materials first and take the N2, then gather new materials and focus on N1?
Bottom line though, JLPT is a better indicator of your ability to take a test than your language ability (though It's perhaps a bit better since they revised the test structure). Once you get comfortable in Japanese, spend some time enjoying it by reading books, watching movies, and talking to people; your language ability will develop naturally, which will make the studying easier too. Worry about the test later, nobody else really cares what "level" you are anyways.
*screeching sound* OK, pump the brakes. I just saw these threads merge and hadn't seen the first one.
ARE you an absolute beginner? Why are you even thinking about JLPT levels? I wrote my response in good faith that you were at least approaching the end of the series and were looking to continue your studies. Have you even STARTED?
Hopefully my response will prove helpful to someone else, cause it seems like it'll be a few years before it's of any use for you @IsaacDavid