Reddit reviews Classical Japanese: A Grammar

It's not easy. Your best bet is getting to a good solid foundation on modern Japanese first and then seeking resources aimed at natives. That being said I can't recommend Haruo Shirane's Classical Japanese enough.

It partially depends on what kind of treatment you prefer, such as how much grammatical and historical explanation there will be.

I'm not sure I know of any resources that are "good".

One that's free is what /u/Pennwisedom suggested: imabi

If you're looking for English resources then Haruno Shiroe's books are the most frequently recommended I think.

Depending on your access to libraries and scholarly sources you might find interesting linguistics articles about it, but that's a lot more work to digest.

There should be lots of materials in Japanese (high school textbooks, websites, etc.), but that might be a bit tough to slog through.

There is a Japanese site with lots of free educational videos (kinda like youtube-y recorded sessions) called manavee. There are videos about all kinds of subjects there.

When you look up older Japanese (typically all lumped together as Classical Japanese) stuff in Japanese, you'll have to look under 古文 (こぶん)

The stuff I know is hobbled cobbled together from lots of places, so unfortunately I don't have a great recommendation :/

Edit: Rhyming words!!! *shakes fist\

I own a copy of "Classical Japanese: A Grammar" but have not used it yet.

Imabi also has a rather extensive section on Classical Japanese.

I recommend reading a book on classical grammar. I used this one and it's quite good. Particles have uses in classical Japanese that don't appear at all in modern Japanese, and there are similar-looking auxiliary verbs that are completely different in what they mean, so it's good to build a background. As far as free online stuff goes, there's imabi, but I'd recommend a book over imabi because it's not very well organized and it's pretty obtuse for a learner.

That said almost all of these will also be defined in a J-J dictionary, which if you already know your verb forms and such, is probably your best bet. It's just a matter of grabbing the kanji-fied form of the iroha poem and looking up the parts that are bungo.

For example (from Meikyo):

を (as in 散りぬるを)

〔接助〕文語

逆接の確定条件を表す。…のに。「大雨の折にも車の贅はやられぬ身成しを、一念発起して帽子も靴も取って捨て〈一葉〉」 ※【表現】「のに」に比べて、論理関係を述べる力が弱く、詠嘆の趣がある。


じ (as in 浅き夢見じ)

〔助動 特活型〕文語〔○‐○‐じ‐じ‐じ‐○〕

① 打ち消しの推量を表す。…ないだろう。…まい。「ただ事にはあら─」「君が才をあまり妬しと思ひながら待たるる心神ならで知ら─〈与謝野晶子〉」

② 打ち消しの意志を表す。…ないようにしよう。…まい。「サルスベリの花が猛暑に負け─と咲き誇る」

Assuming you already know modern Japanese, get this book to learn about the grammar. I also have this dictionary, although if you're living outside Japan, shipping might be expensive. I highly recommend it though, as I haven't found any good online dictionaries for classical Japanese.

When you start out, read printed material, not kuzushiji. I started with Houjouki, since the writing style is simple and the material straightforward. From there, you can go on to poems (like in Kokinshu) or novels (like Genji or Umegoyomi).

I have several more translation posts on my blog now, so check it out.

Try these:

How to read classical Japanese

Readings with annotation, commentary, and dictionary

I used these textbooks when I took Classical Japanese. It is technically designed so it can be used by people with no Japanese knowledge, yet I had taken three years of Japanese before I took the class and it was still a little challenging. I highly recommend them, however. They're worth every penny, in my opinion.
Edit: the texts are all in pre 1946 orthography and sample a wide variety of texts from the year 712 to 1800-something

This was one of the textbooks I used in my classical Japanese class (the other one is the reader with the actual texts, the blue one, which is better to start reading after you finish the red one) and was invaluable in explaining the grammar, its meaning, and providing examples of its use. There are simple tables and graphs out there that just give the info to you (our class was furious when we found that out lol) but it's much better to study it.