Please recommend a top-notch bookshlef speaker

It would be difficult to beat a pair of VonSchweikert VR1 monitors. Check out the review in Stereo Times online.

I second the VR1. I have had a pair since Sept and couldn't be happier. Good bass down to 50 HZ or so, small rear port allows placement in almost any place, and such a sweet, smooth and non fatiguing midrange. The design allows a wide range of listening positions. Deep and wide soundstage, speakers disappear. Great crossover. I have mine on a bookshelf and they are not boomy. Wife loves em! Beautiful fit/finish, great cabinets. Look great without the grills (and generally sound better without). They are very efficient at 89 db and 8 ohms easy to drive. Sound good with any type of music--pop, rock, jazz especially. I am listening to Diana Krall and she is filling the room. I run a 100 wpc Forte 5 and and adcom gfp750 in passive mode. Rotel 971 HDCD for source. Wireworld Atlantis II. ICs are Kimber Silver Streak WBT. I don't run a sub but they would sound really full if you did. You can find a used pair for around 600-700. Negatives: discontinued, and can't bi-wire/bi-amp. They are a bit deep on the shelf, but they work on my 10" deep builtins.

If you have power, a pair of NHT classic 3 might be nice too. They are sealed but really crave current. You'll get more dynamic range out of these guys. I have a pair in my HT setup. I still think the VR1 is more musical. If I could do it all over again I'd get VR1s all around in my 5.1 setup.

Be careful placing things on shelves in cabinets - it will collapse soundstage unless it is done very carefully and quite deliberately (a construction project).

ATC 7s, Neat, Harbeth, Epos all make nice monitors.

For something completely different, if space is critical, try Audioengine 5s.