I have the following Etude books. There are etudes in each one that I like and different levels of playing are in each book. Of the 4 I am listing, the first one starts where a beginner who is at least through book 1 or book 2 would be able to do the first few pages. All books progress as you go along:
Carl Fischer Classic Studies: Alwin Schroeder, 170 Foundation Studies for Violoncello, Volume 1 (Nos 1-80). Instructive works of Büchler, Dotzauer, Franchomme, Grützma her, Lee and C. Schroeder.
I like that this book is spiral bound, or maybe I had it spiral bound (can’t remember, but it is now. I think I paid the store to have it spiral bound when they received it.) I also really like the etudes that I have worked on. They are even interesting to play at the very beginning, less difficult, Etude 7 on page 8 is really nice. I have not delved very far into this book, switched instructors. I really need to get back into it. Challenging bowing. These etudes do progress as you continue.
POPPER STUDIES: Preparatory to the High School (“Höhe Schule”) of Cello Playing, Opus 76, For Cello, (Carter Enyeart), No. 3728, International Music Company, New York
This is a light blue staple bound book. My current instructor introduced this book to me. This book starts out with etudes that are more difficult or advanced than the beginning of the first book mentioned.
Popper is used quite often for cello etudes, from what my instructor says.
A Kalmus Classic Edition, David POPPER, Fifteen Etudes For Cello, Opus 76, K 04426:
This is another David Popper Studies book, opus 76. It is different, though. I bought it by mistake. It is white with black text. I was looking for the first Popper in this list, the blue book. I thought they were the same, but just a different cover, by a different publisher. My instructor was using the blue book in lessons. This version has two cello parts. They do not look like the same etudes as the blue book above. I am not familiar with how etudes, etc are referred to. But they both say Opus 76. This book, any words in it are in German, some with translation. There are very few words, but what few there are are German, with translation. Since there is no lesson how to text, it really does not matter. They are mostly music terms, which are familiar, anyway. I have not done any in this book. They are not beginner etudes, maybe book 3 and up.
Modern Method for the Violoncello (26 Studies of Medium Difficulty) by STEPHEN DE’AK, Volume II, Theodore Presser Company
My instructor gave me this book. He used it when he got lessons. I am very lucky, all his notes are in it! I don’t know if it is available anywhere.
I hope this helps. I really cannot recommend one over the other. But I do like the first book, the blue Popper and the DE’AK, but only because I have used them in lessons, but not very much. We have been doing Bach and it really takes up about all my playing time to get those down.