Newbie looking for an interesting introductory book to telecommunication and signals/data processing
"Telecommunications" is too broad a subject: you could spend your entire life learning about just a small part of the field. However, you mention data transmission specifically; I'll recommend these books:

"Digital Signal Transmission" by C. C. Bissell and D. A. Chapman, Cambridge. This is an undergraduate level book that has very lucid coverage of both the physical layer and larger telecom networks.

"Principles of Digital Communicatios", by B. Rimoldi, Cambridge. This is an advanced undergrad textbook that focuses on the math and theory behind digital communications. A great book if you like that kind of thing.

"Data and Computer Communications", by W. Stallings, Pearson. I'm not the biggest fan of Stallings, but his books are very accessible and cover all the bases. In fact, it might be a good idea to start with this book and then continue with more rigorous books like the first two I listed.