I first started using this to learn Serbian back in 2003. The book is a gradual learning curve and includes the modified Serbian Cyrillic alphabet. Eventually all the lessons are in Cyrillic. I feel Serbian is it's own language with its own distinct linguistic patterns. The accompanying audio CDs (now mp3 files) are extremely helpful in learning the specifics found in Serbian.
Here are a few examples:
1. I understand
Serbian: разумем (razumem)
Croatian: razumijem
2. milk
Serbian: млеко (mleko)
Croatian: mlijeko
3. bread
Serbian: хлеб (hleb)
Croatian: kruh
I would highly suggest this or Routledge Colloquial Series for learning any language. Each chapter has a specific language lesson introductions, travel, ordering food, at the doctor, on a trip. Within each chapter there's dialogue, vocabulary drills, and grammar.
Thanks!