When I first ordered the Colloquial Lithuanian self study course I had my doubts about it. I had just about completed a self study course in German which was completely audio and reading based and was relatively easy which took me about a year to complete and then thought, well, I'll have a go at Colloquial Lithuanian after all I now live in the country. I listened to the introduction and pronunciations at the beginning of the book and then started the first Unit. Then I thought this is way far to much studying and too much work compared to the German course I had just completed, so I promptly stored the book away and looked for alternative way to learn Lithuanian.
Since self study Lithuanian courses are very thin on the ground there is not much alternative so I also ordered the newer version of Teach Yourself Lithuanian to compare with the Colloquial version. The reality is, both are very good learning tools and if followed should bring you to a decent standard of fluency and you should be able to communicate effectively. What Colloquial Lithuanian makes you do is study the language and study the grammar and vocabulary between the dialogue and exercise sections, but after all, Lithuanian is quite a grammatically challenging language. Perseverance and practice is definitely the name of the game here.
I must admit that I do have a big advantage living here in Lithuania and having a wife that is a native speaker and being surrounded by Lithuanian speakers. But that still does not change the fact that Lithuanian is completely different from any other European languages and takes that bit more effort to learn. If you are thinking about buying this book to learn a few phrases before going on holiday then don't. This book is aimed at the serious language learner who is aiming for fluency. I am about three quarters of the way through this book and my fluency is coming along fine but I have been putting a lot of time and effort into it. So as one other reviewer said this language is not for the faint hearted.
If you are looking for a comparison to Teach Yourself Lithuanian I would say Colloquial Lithuanian has the edge over TYS. The grammar points are easy to follow and the dialogue is spoken at a normal speed. Where as the Teach Yourself is spoken at a very slow pace but does give you good pronunciation. But the mind does tend to wander away because it is so slow.
For an absolute beginner that knows nothing at all about the language, not even a single word, it may be worth going through the TYS book first and then read and listen to the Colloquial series. I am using the dialogue from TYS along with Colloquial and has been effective. But for someone with no knowledge at all it worth trying to find or contact a native speaker at the start.
This book is like anything else in this world, you will get back what you put into it. If you put in the time and effort the rewards of speaking a new difficult language will be rewarding. If you don't put in the time ten you will get very little back.
Good luck with your learning. Viso gero!