Of course not, you won't be able to learn Krav-Maga without a teacher.
First, Krav Maga cannot be practise alone, you need a partner.
Second, when you have a partner, nobody will correct your move and says "hey look at your body, it's badly positionned, like this you're exposed to this, this and that...".
Again, martial arts are not important. Krav MAga is not better than another MA. All the difference is the instructor!
You want something efficiency-related: beside Krav Maga, there's JKD, Kali, Thai boxing, Penchak Silat, Pankido (Europe only), etc.
It's just a question of instructor. One will find a good krav-maga teacher and then stick to KM. Another one will find a bad teacher (and bad is relative... it may ba bad for a student, and good for another one), and in his mouth KM will be crap.
You, we build ourselves our way of fighting. We have to learn from any experience, and most of martial arts can bring you something. If you cannot find this kind of style, no matter, take Karate, Taekwondo, Brazilian Ju Jitsu, anything if you feel that the teacher will bring you something. In Karate you may learn some technical basics, in TKD powerful kicks to the body and hip motion concepts, in BJJ groundfighting, etc.
Take your sport bag and go to the nearest club and try.
Cancel the order (if it's not too late).
Guillaume
PS: i don't mean videotapes are bad... it's a complement when you have reached a level of practise in this style