I purchased the following from amazon in 2010:
Greek Septuagint.
It has Greek in a column on the binding side (2/3 of the printed page) in an Oxford font which I prefer, and an English translation by the author/editor on the remaing portion of the page. This is the best layout in my opinion, because interlinears tend intefere with reading the Greek text. It is a quality hardbound book I am glad to have in my library.
The tanslation has close correspondense in the passages that I have studied/translated.
I also purchased this analytical lexicon: Analytical Lexicon to the Septuagint. It could come in handy, if you have better things to do with your time than trying to discover the lexical entry for a form.
I have the same version post 14 refers to:
The text is a photo reproduction, but it is quite readable.
One last thing: If you have a Liddell-Scott Intermediate Lexicon (an abridgement), you might want to get the full Liddell & Scott's Greek-English Lexicon. It too is a photo reproduction, but reproduced well.
My intermediate lexicon was badly worn, so I was happy to finally be able to afford the unabridged version, which I used for my undergraduate degree in Classics back in the 70's. We had one in the reading room of the Classics Department at UCSB and it was a valuable resource when the smaller intermediate lexicon either had no entry or a less-than-helpful incomplete entry.
For the best Greek Langeage copy of the Septuaginta get the copy printed by the Deutsche Bibelgesellschaft and edited by Alfred Rahlfs ISBN 3 438 05121 4. You have to know Greek to read it, or have a computer program which will translate Greek.
It is an excellet book.