Here's the full text of An Introduction to Ryukyuan Languages (2010), ed. Thomas Pellard and Shimoji Michinori. From Shimoji's introduction (yo dawg, we heard you like being introduced to things...):

This book, entitled An Introduction to Ryukyuan Languages (IRL), is a collection of grammatical sketches of six Ryukyuan languages: Ura and Yuwan (Amami Ryukyuan), Tsuken (Okinawan), Ikema and Ōgami (Miyako Ryukyuan), and Hateruma (Yaeyama Ryukyuan). The target readers of IRL are not limited to specialists of Ryukyuan; IRL is open to both specialists and non-specialists including theoretical linguists, typologists, and linguists working on non-Ryukyuan languages. In fact, IRL is deliberately organized in such a way that common typological topics likely to be asked by a non-specialist of a given language (e.g. word order, case alignment, morphological typology, property-concept encoding, etc.) are addressed by all authors [...]. IRL is, literally, an introduction to Ryukyuan languages.

I haven't read the whole thing yet, and I'm not in any position to judge the book's content in terms of accuracy in any case, but I read Pellard's chapter on Ōgami and found it lucid and enlightening. I also found only one non-trivial error, making the chapter literally orders of magnitude more polished and readable than a book from [Prestigious UK University] Press that I spent five figures on earlier this year.

(The error: on page 122, /Ci/+/ɑ/ is said to coalesce to both /Cɛɛ/, but then lower down the list the same combination is said to coalesce to /ɛɛ/. I guess it's possible that this isn't, in fact, an error — that both are true — but in that case I'd expect them to be on the same row and/or accompanied by an explanation.)

Speaking of Pellard, I recently read and enjoyed his Proto-Japonic *e and *o in Eastern Old Japanese (2008), also freely available online.

Adnominal forms with a final /-o/ or reconstructible with an *-o are thus attested in several different (sub-)branches of the Japonic family (EOJ, Hachijō, Toshima, Akiyama and Ryukyuan). Hence this excludes the possibility that these forms are a common innovation. The geographic distribution, with several attestations in very distant and isolated areas, also excludes the possibility of borrowing. [...] Therefore it seems rather unlikely that the adnominal forms arose late in Japonic, as proposed by Frellesvig (2008), since there is definitely evidence for reconstructing the adnominal/conclusive opposition in PJ from comparative evidence.