youngmic,
continuing the theme, consult the POH.
Using the BE58 POH as an example (because it is the ony POH for a light twin that I own) the emergency procedure for engine out refers us to Section X for 'additional information regarding pilot technique'.
Section X says a couple of interesting things that xorrelate to your post. The first is that '......The net result of these forces cause the airplane to sideslip slightly towards the dead engine. This sideslip may be balanced by banking slightly (up to 5 degrees) into the operating engine.'(My underlining for emphasis). Then, in the same section it talks about the definition of Vmca which includes the phrase '....maintain straight flight, with not more than 5 degrees of bank...; (my underlining again).
There is no myth as such, except for in the way many may tell it. The sideslip angle is very bad as it reduces the effective airflow angle of incidence over the rudder, reducing the ability to counter yaw, requiring additional rudder input which further increases sideslip and thus it feeds on itself until you run out of rudder. A slight angle of bank, as the book would have indicated, tilts the lift vector to counter the sideslip vector and normalises the airflow over the rudder.
The issue is that Vmca certification requirments state that not more than 5 degrees angle of bank may be used to neutralise the sideslip. In order to fly away from the ground, you want as much of the lift vector vertical as possible. As you have indicated, the actual AOB required may be much less that 5 degrees depending on the situation. However, it is the Vmca that will kill you in the initial stages and 5 degrees is a good figure to go to (unless the POH sates otherwise) until you are happy that you are maintaining directional control and can assess the situation further. As to how you identify the required angle, I believe that the skid ball should 'point to the ground' when the sideslip is neutralised (ie, slight left bank will have the skid ball slightly left of the centre, about half to one ball). Once you get a margin above Vmca, rudder authority isn't as critical and you can trade-off sideslip to get a better rate of climb. Whether this is desireable or necessary will depend on the advice of the POH.
So, yes, the book is correct, and 5 degrees is correct as a certification figure, and for the aircraft you are flying you should always refer to the Emergency Procedures section of the POH.