A scientific understanding of how genetic modification works is helpful when approaching this topic. I would recommend High Tech Harvest: Understanding Genetically Modified Food Plants, by Paul Lurquin. It's not exactly light reading, but it takes you from Mendelian genetics to modern biotechnology. If you ever wondered exactly how they get those genes in the plants, this book explains it. Surprisingly, it can involve "gene guns" that are, literally, guns.
The ethics of biotechnology are a complex subject. Some people claim that the risks are too high. Although risks obviously must be considered, they must also be weighed against the benefits, which could be considerable. A good book on this topic is Seeds for the Future: The Impact of Genetically Modified Crops on the Environment, by Jennifer Thomson, which is essentially a literature review of studies on the risks and benefits on genetically modified crops. (This book may be difficult to find, if your public library doesn't have it, a college or university collection probably will.)
In this book, the author outlines many concerns about genetically modified crops, but she most often concludes that the problems with genetically modified crops are no greater than those caused by conventional crops. Although this might sound unlikely, she makes a convincing argument that in general, it is modern agriculture which harms the environment, not the type of crop planted. In the end, she concludes that regulations need to be in place (as they are), and that in some cases, biotechnology lessens the environmental impact of agriculture, by reducing harmful chemical use, reducing the area of land under cultivation, while simultaneously improving the health and income of many farmers, especially in developing countries.
As an African, the author's perspective is largely focused on the potential benefits of biotechnology for the developing world, which cannot be ignored because people in developed nations feel squeamish. She paraphrases from a report by Per Pinstrup-Anderson (former Director General of the International Food Policy Research Institute): "Condemning agricultural biotechnology for its potential risks without considering the alternative risks of prolonging the human misery caused by hunger, malnutrition, and child death is as unwise and unethical as blindly pursuing this technology without taking into account the necessary biosafety regulations".
The future of genetically modified plants is astounding: plants that withstand extreme drought or other environmental stresses, "golden rice" that provides vitamin A, possibly preventing up to 3000 deaths per day and 500 000 cases of infant blindness each year, plants engineered to produce vaccines that can be orally administered, making them much more accessible to developing countries, plants that can remove heavy metals from contaminated soils, and even plants that can fluoresce when they detect the presence of TNT in land mines. Some may disagree, but I believe that this is a technology that deserves continuing research.