L.A. County Assessors Mapbooks - on the way to Jamboree

After spending three weeks in Turkey on a travel tour, (and seemingly the same amount of time flying to and from there), I'm zeroing in on Southern California getting ready to attend the Southern California Genealogical Jamboree in Burbank, June 8-10, 2012.   So as not to waste any precious time in the Southern California area, I've already stayed two nights in Chinatown, so as to be close to the Los Angeles County Hall of Records.  I spent two "head-ache inspiring" days down in the bowels of the Records building - in the subterranean dungeons of the "Archives" area.  I came here last year for divorce and probate records of my family who have lived here since 1903.  This year I wanted to search more into the land records.  While the actual land records are in the County Recorders Norwalk office, which I visited last year, I wanted to find anything more about the early land records to find the actual deeds..... something so easy to do in small counties of the US...  but not in Los Angeles, County.    Although the clerks at the Mapbooks office had nothing else to do but help me, (no other customers, they just chatted) they didn't offer any insight as to how their records might be helpful. I'm pretty certain they really didn't know that much about what the books contained.   They were the keepers of the "Los Angeles County Assessor's Mapbooks" and keep them in order and pull them.   Mapbooks show the tax values of a certain piece of land, and they don't go by name or old address.   Without some kind of asseAssssor ID number, or some such thing, you can't get into the books.  But you can if you have the CURRENT address of the house/business/warehouse/etc., that NOW occupies the lot of land that was once an address in question (in this case those of my great-grandparents) 1766 E 21st Street  and 1674 Stauton Ave. Los Angeles.  Both have been gobbled up by industry and those addresses no longer exist.  That presents a problem for the keepers of the mapbooks.
             That night I looked up their LA County Assessors website online and found a couple adjoining addresses and sure enough, the next day with the neighbor addresses  they could find the land lots.  What you see is a tract map of the property and on the facing page, a list of the owners of each lot in the map of the block, or whatever.  The book may cover 1 to 10 years, depending on how much space the book has.  Its lists the tax value for each year, with lot and parcel number assigned to each owner.  If there was a sale, the new owner's name is written to the right of the old owner, but in the older books there is no DATE of the transaction.  So it might be anytime during the length of time of the book.   Is that clear???    Definitely head ache provoking.
    With high piles of assessors mapbooks brought to me, I dutifully went through each one, like a title search.  I think I was looking for an Assessors ID Number.  Something that doesn't seem to exist for these records of early 1900.  And there was no nicely added date of any land sale/transfer.  As I went down through the books I hit a dead end for both the addresses as the note on one books that says "where to look for the prior book" came to an abrupt end - with "Dead Page" being listed on the computer that the Keeper of  the Mapbooks looks at.   So my search only went back to 1940's on those addresses.    
    I'm going to return to the Norwalk office to see if there are any more "deed-like" documents I can find there, beyond what I found last year.  
    Hopefully when I get to the Jamboree in Burbank I'll have found some more information on the land transactions of my great-grandparents - Frank and Edith Blanding.