In Italy Vaccaj's (with J not I) volume is available in a Ricordi edition edited by Mr Battaglia, but I guess and hope the real content, meaning the wonderful little arias, is just the same here.
First of all, unless you already have a clearly defined vocal range, I suggest you buy the edition for mezzo/baritone (especially not the high soprano one), whose range is really a medium one and is suitable for nearly every kind of voice. Later on, you shall buy the edition more suitable to your register.
This small booklet is small in size only.
A beloved textbook, it should be the basis for anyone wishing to train as a singer.
The short, apparently simple arias, are the masterpiece of a genius didactitian: every note, every interval, every sillable of the text is perfect and perfectly suited to educate the inexperienced singer. Those who despise the text as too simple should be ashamed of their musical skills: there is nothing simple here. The arias can be sung by beginners but to sing them properly you have to be a perfectly accomplished artist.
Once you have completed the course you will be able to declare yourself competent in singing.
Another fact is that the arias are beautiful. Vaccaj was not a great composer but he was a wonderful craftsman. All the short arias are small gems, very pleasing to the ear, with nice piano score.
Last but not least this method will be extremely useful to pianists too: technically it is not difficult but it is a wonderful way to learn how to accompany a singer, a very difficult skill.
I have been using this method for the last couple of months and I cannot get tired of it. You will have the most useful buy of your singing career for very little money. Do not miss it.