
Japanese: The Spoken Language (JSL) is an introductory textbook series for learning Japanese. JSL was written by Eleanor Harz Jorden in collaboration with Mari Noda. Part 1 was published in 1987 by Yale Language Press, Part 2 in 1988, and Part 3 in 1990. The series differs from most Japanese language textbooks in many ways, most basically in that it focuses exclusively on the spoken language and leaves discussion of any aspect of the written language to other textbooks, such as the parallel series Japanese: The Written Language (JWL).
my book is more an encyclopeadia of the grammatical constructions used in Japan, organized by broad category, which you can cherry pick parts of to supplement whatever topics you're covering in your regular course work, or leaf through when you want to refresh your understanding of the grammar.
Books like Nakama, Genki, Japanese: the spoken language, etc. are great (although I don't like how many of these books don't use hiragana after the first few weeks), and then having a cheap grammar (this one's free, or $30 at most if you want a copy you can leaf through) alongside it only helps you get a deeper insight into the learning you're doing in your school or university course, or even your spare time.
If you put a gun to my head I'd say find yourself a copy of Japanese the Spoken Language with the CDs and drill them until your ears bleed. In particular, make sure you practice production (i.e. talk, talk, talk, if you don't sound like the CD keep talking until you do, then drill some more). The lack of somebody to tell you "You're saying everything... wrong" is one of the largest problems with self-study.
The largest is that almost everyone gives it up.
This is the exact problem with learning Japanese using roumaji (rouma ji = roman character; ローマ字), because you of course start to read the latin script with your starting accent (assuming of course your first language is written using the latin alphabet).
However some textbooks persist with using it, despite being excellent otherwise (Japanese: The Spoken Language being one). I can't stress enough the need to move off reading Latin characters. It is also useful to learn the characters by sound rather than their roman equivalents. i.e instead of learning that ロ is "ro", you could learn it by listening: https://youtu.be/aLEtZ2CRoho?t=1m53s
The mental association is everything.
Even textbooks that used to use romanized Japanese for fairly logical pragmatic reasons, like "Japanese for Busy People," which is aimed specifically at busy adults who are trying to learn the spoken language in the least amount of time/effort, have been rewritten to eliminate romanized Japanese! Many people studying Japanese go so far as to consider the presence of romanized Japanese, even in combination with normal written Japanese, a black mark against a book, a viewpoint which I think is a bit extreme.
Additionally, even if there is a benefit to early spoken fluency, it's going to really annoy students when after two years they suddenly have to start learning the writing system from the very beginning. With this approach, students wouldn't be able to use any modern instructional or reference materials for 2-3 years. Basically, they wouldn't be able to study on their own at all.
Also, from the standpoint of practical language instruction, since many students drop out of Japanese classes the second they're asked to learn hiragana (much less katakana and kanji), it is much more efficient for all parties involved to have this occur earlier in the process.
Many people studying Japanese as a foreign language actually also 1) find it very discouraging to discover that they can't read words they know because they haven't been taught the characters, and 2) find it very difficult to parse romanized Japanese since it is harder to tell where words end and distinguish particles/verb endings from nouns and verb stems.
http://languagelog.ldc.upenn.edu/nll/?p=11580
> The problem was that all of my language teachers insisted that I memorize hundreds of characters right from the very start.
For every person who is mad that that they were made to learn kanji from the beginning, there is another who thinks their Japanese ability was permanently impaired by not being taught kanji early enough (I have met plenty of the latter). Regardless of the method, there are people who are going to object to it.