Rilke's letters to Franz Kappus were written between 1903 and 1908. They were first published in German in 1929. In 1934 H. D. Herter Norton produced the first English translation (revised by her in 1954). The second English translation that I know of was done by Reginald Snell in 1945 and published in London by Sidgwick and Jackson. The edition being offered here is the Snell translation--only his name and the original publication data have been stripped from the book. (Other than that, the book is essentially a photocopy of the 1945 edition.)
The publisher here is "BN Publishing" which I assume means "Barnes & Noble" (although the "about us" link on their website says almost nothing about them!).
The Snell translation seems to me quite adequate. Here is a sample of one sentence done by three translators:
"And this more human love...will resemble that which we are preparing with struggle and toil, the love that consists in this, that two solitudes protect and border and salute each other." -- H. D. Herter Norton (1934)
"And this more human love...will be something like that which we are preparing with struggle and toil, the love which consists in the mutual guarding, bordering and saluting of two solitudes." -- Reginald Snell (1945)
"And this more human love... will resemble what we are now preparing painfully and with great struggle: the love that consists in this: that two solitudes protect and border and greet each other." -- Stephen Mitchell (1984)
Of these three, the Norton seems to me to have the best cadence, but beyond that Rilke's sense is present in all.
One does wonder, however, why BN Publishing felt free to erase this book's origins.
One other oddity to note: If you click on "see inside this book," Amazon shows you the Stephen Mitchell edition, not the Snell edition, giving this rather confusing explanation: "This view is of the Mass Market Paperback edition (1986) from Vintage. The Paperback edition (2009) from BN Publishing that you originally viewed is the one you'll receive if you click the Add to Cart button at left."