Jim,
but shouldn't the DCS manual cover it's needs
The DCS manual covers less than 50% of DCS as compared to The DCS O Gauge Companion 2nd Edition.
The DCS manual is 119 pages in a 5" X 7" format while The DCS O Gauge Companion 2nd Edition is 215 pages in an 8" X 10" format,and the font size is about the same.
The DCS mania; is black and white while The DCS O Gauge Companion 2nd Edition is full-color.
The DCS manual is a very basic guide that pretty much states what pressing each button on the remote does. The DCS O Gauge Companion 2nd Edition is set up as both a tutorial as well as a reference manual which explains not only what buttons do what, it also discusses why things work the way they do.
The DCS manual discusses MTH engine operation via the remote acceptably enough to get someone started using DCS. TMCC is discussed in a couple of pages. It does not discuss AIU operation, switch tracks or accessories at all.
The DCS O Gauge Companion 2nd Edition discusses everything in-depth, and also discusses how to connect Lionel command bases (both TMCC and Legacy) separately or together; use of the AIU to operate switch tracks and accessories; and connecting switch tracks and accessories from both MTH and other manufacturers.
With thee exception of a couple of simple wire to track connection diagrams, the DCS manual's pictures are solely those of greyscale DCS Remote screens. The DCS O Gauge Companion 2nd Edition has 64 figures, many in full color, that actually illustrate how to do things, as well as 10 Appendices tag provide reference material that does't exist elsewhere.
The DCS O Gauge Companion 2nd Edition include sections on the DCS Commander and DCS Remote Commander. The DCS manual does not.
I've attached a table of contents and a table of figures to this post. Feel free to download them and peruse them to see what makes this book unique.
Then, make up your own mind as to as regards its usefulness.
Everything that you could want to know about DCS and a whole lot more is all in MTH’s “The DCS O Gauge Companion 2nd Edition", available for purchase as an eBook or a printed book at MTH's web store!