I would suggest giving them free rein to choose a short story from Roald Dahl's collected stories or, for example, Sarah Hall's more recent collection 'Madame Zero', but I don't fully grasp the equation between your students' geographical background and their linguistic competence unless there are socio-economic factors to consider as well. What type of review are they going to write--academic-oriented or goodreads-ish? That might also help!
My recommendations for "easily understandable novels" are The Old Man and the Sea, for which its author, Ernest Hemingway, was awarded the Nobel Prize in Literature for 1952, and The Pearl (1947), by John Steinbeck, who won the Nobel Prize in Literature in 1962. Since both of these narratives are relatively short in length, they are really novellas; however, they are usually published as autonomous, independent prose fiction narratives because they are too long to be included in anthologies of short fiction.
I have assigned The Old Man and the Sea and The Pearl as required reading in introductory English Composition and Literature courses which I taught at the university level. My students, recent high school graduates taking the course to fulfill a four-year college graduation requirement that is also a prerequisite for any and all of the literature and writing courses offered in the English Department, seemed to enjoy my lectures and participated enthusiastically in the class discussions. In addition to learning about realism in imaginative literature, the students contributed to the class discussion their perceptions and insights on a wide variety of topics from the role of the individual in the natural world and in human society to economic, social, psychological, sociological, and related themes and issues of contemporary interest. My required assignment, the writing of a 500-word to 750-word theme about some aspect of the texts, whether personal, literary, or other, sometimes led to some of the students making the selection of one or both novellas as the subject of their double-spaced five-page handwritten or typewritten term papers, usually due during the week before the final examinations.
I suggest Ray Bradbury's Dandelion Wine. The book's setting in small town America may resonate with the rural backgrounds of your students:
An entire summer is seen mostly through a young boy's eyes as a time of joys and sorrows. He is imaginative, fanciful, and occasionally meditative on the state of the world. Most of the time, he aims to have fun as a 12-year-old kid, but sometimes he lapses into philosophical brooding on topics, including life and death, more mature topics than what would be expected of his age. The main character, according to Bradbury, draws upon his own younger self. -- from Wikipedia, with slight modifications.
Popular novels are - The Animal Farm by George Orwell, Of Mice and Men by John Steinbeck, The stranger by Albert Camus, "The Alchemist" by Paulo Coelho, "We Have Always Lived in the Castle" by Shirley Jackson
Contemporary: "Less" by Andrew Sean Greer, "Exit West" by Mohsin Hamid, "Convenience Store Woman" by Sayaka Murata,
"The Room on the Roof" and "Vagrants in the Valley" by Ruskin Bond