"The Passing Scene, London, Portsmouth and the Isle of Wight" published in 1926 to coincide with electrification of the London to Portsmouth line.
Although not actually published by the Southern Railway, one of the better known route guides, "Mile by Mile, Waterloo edition" was written and published by Stuart.N. Pike. MBE in 1946 and contains a description of all lines from Waterloo to Portsmouth, Weymouth and Devon.  I have included it here for completeness and it should also be noted that a facsimile version printed in 1980's can be quite commonly found.  The one pictured above is an original 1946 copy.

Recreational guides
"Golf in the South" written by E.P. Leigh Bennett, who was a magazine journalist employed by John Elliot initially to write a monthly article for the season ticket holders relating to train services called "Over the Points", this led to him also writing a number of Southern Publications as seen here.

The version of Golf in South illustrated above was published in 1935. One of a number of editions of this book, the origin of this publication can be traced back to pre-grouping days. They contained information on all golf courses generally within the Southern Railway area. Some of the later golfing publications also included information on courses on the continent and how to get there via Southern Railway Services.

"Fishing in the South" by J.W.G. Tomkin, wonderfully sub titled "when the wind is in the south it blows the bait in the fishes mouth", providing information of rivers and fishing locations with the Southern area and how they can be reached by train, licenses, tackles shops and nearby hotels.   It also contains articles on coarse, fly and sea fishing by contemporary experts.

"Yachting on the Sunshine Coast" was published in 1932 written by a contemporary yachting author Chas. Pears R.O.I. and provided details of suitable ports of call along the south coast for yachtsmen, including information on sailing clubs, mooring locations and charges and of course the access to these location by Southern trains.

"Come Abroad with Us" another E.P. Leigh Bennett written publication was published in the early 1930's describes a number of European Cities and locations to entice passengers to use the Southern's Air or Shipping services.

"Devon and Cornish Days" again written by E.P. Leigh Bennett was published in 1935. Provided information about the towns and resorts in Devon and Cornwall served by the "Atlantic Coast Express and other trains of the Southern Railway" such as Padstow, Tintagel, Westward Ho! and Lyme Regis etc. Colour plates of paintings of local scenes illustrate the book. There is an amendment glued inside the front cover that states "Page 36. - Since going to press the Lynton and Barnstaple Railway has been closed and passengers now travel by motor bus instead."

War Publications
"War on the Line" by Bernard Darwin was published in 1946 as a factual account of the effort made by the Southern Railway to keep trains running during the war.  Includes details of bomb stoppages and the time and effort taken to reopen lines, and an excellent chapter on the heroic Operation Dynamo to move the thousands of servicemen from the south coast ports during the Dunkirk evacuation.

Although not an official Southern Railway Publication, "It can now be revealed more about British Railways in peace and war" was published by the British Railways Press Office in 1945 (bear in mind that all British Railways were under state control during the War). This booklet gives a brief illustrated account on the immense work carried out by all the railway companies during the war.