I am looking for a good textbook that can be used to teach 'research methods in information systems' to both undergraduate and graduate students. Any suggestions ?
Robson & McCartan, 2016 - Real World Research. Not specifically for IS students but a very good all-round research methods text which is readable and contains good examples. If you mean 'Information Systems' then I think this would be ideal, especially for pg students. If you are actually talking about IT-related projects, then this may not be the best text but I am not able to suggest another. For undergraduates, Bell and Waters, 2018, Doing your Research Project may be better.
Books for research Methodology: 1-Book – Research method in Management – Cooper and Schindler, Magro Hill 2-Research Method in management – 8th Edition Willim Zikmund, Cengage Learning
I can highly recommend "Scientific Research in Information Systems" (2013) by Jan Recker. It is very concise and practical. Link: https://www.springer.com/de/book/9783642300479
If you are interested in design science research, which has become a popular research paradigm in information systems, I would recommend "An Introduction to Design Science" (2014) by Johannesson & Perjons. Link: https://www.springer.com/de/book/9783319106311