Alry publishing has this exactly right - not masterworks but great to play. One of the pleasures in approaching this book is unearthing now forgotten repertoire as well as finding more familiar gems in a different setting. Doppler's hand will ensure that each opera is a bit of a challenge, even though the arrangements are very good. The Barber of Seville is wonderful but my own favourite is Zampa - check it out!
Composers such as Doppler and Nicholson made use of the new-found velocity [in the advances made to the mechanism of the flute] in expounding with great flourish upon the themes of familiar songs. Many have said that these selections lack real musical validity. Granted, they are no masterworks; however, they are exciting to hear ad thrilling to accomplish.